If it is ringworm you'll have a larger problem on hand because it's highly contagious. It's a fungus, not a worm/parasite. Is found everywhere, soil included, thrives in moist/warm conditions. Spread by direct contact, meaning all deer that are together would spread it among themselves and of course contaminate the premises, feeder/waterer and it also spreads to humans. I know of spray or ointments only, nothing injectable. Maybe somebody else knows of something?? Ringworm would look fluorescent under a black light or scrape off sample and have it examined under microscope. Very persistent stuff. I wonder if any garden fungicide would kill it???
Maybe check with vet? Hope it's something else, because it takes constant treatment for weeks even after it's not visible anymore or it'll be right back. No clue how you could treat a deer that doesn't let you touch it.