Hi Hunphrey123 and welcome to TCS!
Good to take him to the vet.. it's way too hard to see what it is but it does need to be checked. It could be ringworm, which is very contagious. But it might be something very simple.
Let us know how you go.
If it's ringworm he would have had more of them appear by now, they spread like wildfire. One spot can turn into 6 in one day. it looks like a healing wound to me, he either got caught on something or if you have another cat, got in a small fight. They lose their hair around bites and scratches. It's not an open, oozing sore, so it should heal fine.
Welcome to TCS! Unfortunately it's a bit difficult to tell from the picture but the good news is it doesn't appear to be infected. However, it's always best to speak with your vet and ask if he should be brought in for observation/treatment. Better to be safe than sorry!