I have worked as an urban planner, and am a certified plans examiner and zoning inspector, and life safety code/fire inspector in FL.
First thing to do is, contact the supervisor and code enforcement officer or member of the department that gave you the notice of violation. Be polite. Write to them and ask for a month of time to get a local business to take care of this for you, because they can't deliver your rock to your prepped site within the timeframe the community mandated.
The city/county/etc. should normally grant your request. #1, you have acknowleged the notice of violation, you #2, have contacted a local business about bringing you fill, you #3, have recognized the need to contain the crushed rock via site improvements, and #4, you asked for a reasonable timeframe to accomplish the work. Even if you intend to do this entire project yourself, do this/tell them this.
All the local government is interested in is seeing the local code followed. Be glad they are not asking for a 'paved surface connecting to a thoroughfare or surface street,' something many jurisdictions do!
In the interests of maintaining relations w/your neighbor, do not fall prey to the idea of retaliation. Local judicial bodies will recognize it for what it is and you are just going to pick a scab that can easily become infected. People get shot over things like this that just escalate, you don't need to have your life negatively affected by seeking retribution, even though there would be a satisfaction quotient to stuffing his face into a steaming pile of canine or bovine manure.
Follow the steps I told you and you will be able to put it behind you, and return to your life apart from such issues. It is easy to sink into a neighborhood war of retribution, and all that will do is make you miserable and possibly end very badly.
If you want to know exactly what you need to do, go to your local jurisdiction's website and at either the Building Dept. or Planning & Zoning Dept. website section, you should find some-sort of link to city or town or county code of ordinances. Use the search function to investigate topics like parking of recreational vehicles, trailers, or boats, and driveways. Use any or all of those to find what your requirements are under the adopted ordinances. You will also be able to find-out what your property's zoning classification is which is what tells you what part of the code of ordinances covers your property. There will probably be a link to a GIS map which shows your parcel specifically. Sometimes it is located at the property appraiser's website under a tab for maps and aerial views, or something similar. Note that there may be one clasification for zoning and another for future land use, which is required for areas of population where the housing is more-dense, i.e., urban areas. They may-be the same in name, but they are not the same, nor do they mean the same! For instance, a zoning district of residential, density of two dwelling units per acre is not the same as a future land use classification of residential, low-density. The zoning classification is what governs your building requirements.
Working from a point of knowledge is far-better than trying to stumble-along and making expensive mistakes because you bought the wrong grade of rock or didn't install a required method of retaining the parking surface material, such-as curbing, landscape timbers, edging, or whatever is required. It's worth a trip to the Building Dept. to get an OK on your proposed materials and method of installation. Be forewarned, many jurisdictions require appointments to speak with the plans reviewers or other professional staff.
I suggest you bring a copy of your survey which you have photocopied multiple copies of, and show on it where you want to place the material, drawn as-much as possible to-scale. This will also help you to estimate how-much material you need when contacting a local hauler of materials. Get multiple bids on what you choose to use, as you may find a great distance between jobbers. They may have a minimum size load for-which you have to pay, even if you only need a fraction of the carrying capacity of the delivery vehicle. Also, they may not be able to deliver exactly where you want it, especially if you ask them to place it off a paved road. Haulers are occasionally seen on the 'net having sunk to their axles in a drainfield, or a septic tank, or straddling a wellhead, gushing water from the broken pipe onto the property, and the truck sunk in the soft earth. And don't we all laugh whan that same truck topples sideways or slides down a change in elevation, and inverts? We all laugh until it's on our property!
I've seen all these things and more, and I have had to do tactical rescue when they happen. Plan before you act. It's less-costly, safer, and will reduce the stress you have already encountered dealing with this. You can PM me if you have a question.:ummm: