How are you managing the different heat zones?
But, I wonder if he got that sore by rubbing his nose on the walls of his former glass walled hab. It's a pretty common injury, and when they get infected can be devastating to their faces. I've struggled with that in the past. If it gets worse or starts to spread or bleed, he should immediately see an exotics vet to prevent gangrene, and the bottom 6 inches of the cage walls covered with something he can't see through (cardboard) to stop any secret rubbing.