I suggest that you see a qualified (experienced with herps) vet A.S.A.P.- & this site can help you find one: https://members.arav.org/search/custom.asp?id=3661
I recommend NOT using "castles" & such decor designed for tropical fish in snake enclosures, because ones I've come across have very sharp edges left inside, here & there, which apparently doesn't bother fish but can cut up a snake pretty bad if they try to wedge in for a sense of security, or can cause a very infected puncture wound to a snake that's just innocently exploring. I would not think "allergic reaction"...much more likely a small infected cut. (And did you wash & disinfect the "castle" first, before putting it in his home?) Personally, I'd donate it to someone with fish.
I wouldn't be eating either if my face was comparatively as swollen as your snake's face is. Ouch. And head infections are near vital functions (eating, breathing, eyes, brain...BRAIN) so infections can get serious pretty fast if ignored. And if you don't know, snakes generally have solid pus, so infections don't drain without help- they require the delicate surgical skills of a veterinarian to to remove abscesses, which might be what this is. Left alone, infections can spread too. Your snake likely needs antibiotics...prescribed correctly from a qualified vet.
95* F. is too hot- can make a bad situation worse by causing thermal burns to your snake. And temperatures too cool can mean the snake's immune system won't function so well -ie. they can have more trouble fighting off an infection. Very important to get the temperatures corrected & reliable.