It's definitely not ringworm, because it's already drying up. I THINK it might be a little "burn". Butchie, who you all know is nekkid (no fur) sleeps in a kitty bed near the radiator. He MAY have fallen asleep with his back up against it and that's how it got there.

I cleaned it with Hydrogen Peroxide Wipes and put Triple Antibiotic Cortisporin on it. He's good about it. I think I'm making more of a big deal out of than he is.