Somebody might have backed the side of her "One" into the owner of the nursery she works at truck door - it's a long story, and the owner of the nursery is at fault NOT the owner of the "One". Seriously. Has anybody used "Dr. Color Chip" that advertises in Roundel? There isn't enough damage to necessitate having to spray the entire wheel well, but there is a spot of expose black plastic that is driving me insane already. Help!
I haven't used it, but I have heard it recommended by others. I have a can of OEM Alpine White III sold by some outfit that sends you paint in a pressurized rattlecan... but have not had the time to apply it to the roadster. They sell clearcoat, too.
If it's more than a dab, take it to a good paint and body shop. In the long run, you'll be happier and wont place the rest of the paint at risk.
Probably a pic or two would help. Use a coin or ruler to show scale. I am not clear how you damaged your wheel well backing the side of your "One" into something. Is the "black plastic" the wheel well liner, or exposed bare trim? The wheel well is behind and around the wheel, but has no surfaces on the rest of the exterior body. I have used Dr. Color Chip with excellent results on small spots, but anything bigger than this: big is too big for it. Clear coating it is really hard to do, because you blend the base color with their SealAct, and you can't do that with clear coat, so it has to be small and unobtrusive. Feathering clear coat, wet sanding, and polishing it out are very difficult without expanding to edges/borders or re-doing a whole panel. Nurseries are notorious for attacking Bimmers with their buildings and trying to pin the blame on the drivers! The best revenge is to take your annuals back for a refund after they expire seasonally, or drive a Honda or Toyota right into the offending door! (or any British car that is actually still running will do nicely too). However, unless you are OK with learning the DIY with trial and error on your "One", I recommend paying a pro even if it is a small ding. Good Luck.