Smudge Saga

OK, I'm having a kitty crises again.

Smudge has been a bit off-colour the last couple of days and I noticed his head was sore. I kept a eye on him, but he seeed OK, just quiet. Today I've just seen pus on his head - by the looks of things it's an abcess which has burst. Can someone please tell me how to clean it up? Just use a cloth? In hiself he seems much brighter now, but I want to make sure its all out.

Thanks.