He either has a skin infection, or a parasite like fleas. Bring him to the vet to find out the correct treatment. if he is scratching near his ears and his ears have waxy buildup, he most likely has ear mites. The vet can very easily give you medication for this :) also, if he has a bad scab there, he might've gotten a scratch which itched as it healed. my cat did this. the best thing to do is just to stop him every time he stars scratching it, and maybe even put a cone on him if needed. if you can't afford a vet, call them anyway to ask for advice.