pics may help us figure out what is going on, but my guess is that its a burn from the heat rock, they will often over heat and cause burns, I do not use them at all for my herps. When you said you "boosted" the rock, did that me throw it out? I would put him on unprinted newsprint or paper towels, and keep it very clean! If it is feasible a vet visit would be a good idea, at the very least, if you don't have a vet you already go to, start looking for one in case this gets worse. As far as the stargazing, not sure, could be a reaction to pain? Keep a close eye on the wound, and head to the vet if it gets worse, as someone who has pulled maggots out of a burn caused by a heat rock (at work, not one of my herps) you do not want it to get worse!
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hanging out under heat lights burns up my brain cells!!