Thanks ladies.
We're taking him to the doctor this afternoon so we'll find out for sure then.
It doesn't seem to be bothering him at all. He never scratches mozzie bites either though. So who knows.
He's happier today than he's been all week.
He's ate breakfast normally and is breastfeeding fine so hopefully it's just a mild case.

How long does it take to clear up?
Is it uncomfortable, itchy, sore?