Does anyone know what this is?

[Sleepinglemon]

My cat has what looks like a scab and (presumably self inflicted?) bald patch on his forearm. We use flea treatment from the vet regularly and haven't spotted any other sign of fleas. Just wondering if there's anything else it could be other than over zealous grooming of an itchy flea bite?

Could be a bite that has abcessed

I don't think it's an abscess. It's scabbed over and he's well in himself.