Hi. It is hard to tell from that pic if it could be ringworm. It could also be a place where he has scratched himself raw, from itching. Although not highly likely, if he was on meds for his flu/fever it could be an allergic reaction. It is less likely to be ringworm, unless he goes outside or has been exposed to another cat/pet/animal that has it.
A home remedy to see if it will clear up on its own would be to buy chamomile tea bags - typical grocery store brands which are almost always German (you don't want English, nor any additives/flavorings) - brew a bag in water, cool the liquid, and dab it on the spot with a cotton ball or soft cloth, multiple times a day. The tea is both a soothing and healing agent, and has anti-bacterial, anti-microbial properties. It is safe for him to ingest as well. This won't cure ringworm, but if it is just a scratch, it should help heal it.