Eventually, with taking the wheel on and off a bunch of times, the paint on the drop out gets scratched and chipped. This, however, looks a bit excessive.

Drag out a flat file and get to work on trying to smooth the outside of that drop-out. Better yet, go back to the shop and ask them to do it for you since they contributed to the damage in the first place. Try not to remove too much material. Work it a bit and try the wheel again. If it still slips, or drops into that groove, work it a bit move.

If you're really worried about how it will look after, coat the bare metal with some clear nail polish. OR dive into your closet and find that black nail polish you still may have from your Goth days in college. After you touch up your drop outs, you can do your nails and go shopping! Might ease the pain a little.