I had a feeling it was a burn, the pus bubble looked like some I've had from bad sunburn and furnace incidents.
I've rearranged his lamps and uvb to prevent any worse from occurring. I have it about 10 degrees cooler now, he's not happy about that it seems, but he'll live at least. I feel dumber than I was, I knew the dome lamp I picked up was going to push more heat than the wire framed one but I didn't think it would be that much higher.