Ringworm will glow under a black flourescent light. If you can get your hands on one (veterinarians have them), check for it that way. If it does glow, it's ringworm. Go buy Myconozole cream (for athlete's foot) and rub it into the area 3x/day. Make sure you wear rubber gloves and keep the cat isolated from everyone including any children, as ringworm is highly contagious.