Anything in the cage he could have bumped into too hard? Corners? Pointy? Sounded like it was inside his eye at first.

It appears to be just a fleshwound, so there's not really anything you can do but put some sort of antibacterial ointment on it. NO PAINKILLER.

Can anybody tell me WHY no painkiller? It's always the advice, but I've never seen why.