If your nitrided top is starting to look scratched and worn, that’s normal. When nitriding, only the top .0002” or so is even affected. And something as simple as laying a wet towel can damage the surface. Generally speaking, you can just completely ignore it.
If your nitrided surface has pits and other physical issues, you can selectively use a flap disc to remove protrusions, and you can weld in filler material to plug gouges and then use your flap disc or a sanding block to flatten them back to surface level. If you had a big enough milling machine, or even a surface grinder, you could absolutely just shave a little off the whole thing without any ramifications.
No matter what you choose, just follow our simple tips for protecting the surface from rust and it’ll still last forever.