What is this?

[DVirginiana]

Unfortunately I don't have anything regulating it atm, but I felt it and there's no way it could've burned it. I also am cleaning his cage and the side of his water dish felt gooey, any idea?

UNPLUG IT NOW and leave it unplugged till you get a thermostat to regulate it.

They can fluctuate rapidly. 100 degrees won't feel hot to you because your body temperature is close to that. It will feel burning hot to a snake though. That looks like a burn.