Sore on face

I have searched the threads on sores, but I'm still unsure. This morning we noticed a little red sore between Chessy's right ear and eye. He's indoor only, and Emily has never hurt him before, although they bat at each other in play sometimes. Can I keep an eye on it for a few days or should I take him to the vet asap? He isn't scratching at it and doesn't seem to be bothered. Also should I try cleaning it with saline solution? Thanks!
These are the best pictures I could get (he's squirmy):

Cleaning it with a little saline solution would probably help it heal. It does look like either his friend got him or he had a suddent itch and scratched himself. I've seen other cats with the same type of sore, and they always seemed to heal just fine.

Thank you Cloud Shade!