So sorry - i have a ambilobe panther who is the sweetest thing. He loves to come out and sit on my shoulder and hang out. I would be devastated if anything happened, so I understand.
I always knew they gaped when too hot, but then i noticed my cham gape when it wasnt too hot. I didnt understand why at first, but once it happened again it seemed to suggest the a large hormworm was the common factor. Again, just something I have seen and have a theory on.
Ive seen this before and my best guess is that sometimes when a cham is over-hydrated that open their mouths and gape because it's basically acting like a dehumidifier. Too much water and they want to evaporate some. Just from my personal observations specifically with hornworm feeding.
hope he gets better soon and everything works out...trust what you see...you should see healing begin to take place in a matter of days; if that isnt happening or it gets worse, call that vet back!
So...I would probably classify this as an emergency. Get a vet appointment with a vet who knows reptiles.
In the 3rd and 4th picture you can see how underweight he is.
Make sure he is hydrated, hydrated, hydrated. If he has mouth-rot it will likely impact his eating, and that may account for...
Looks like an infection of some kind - hard to know from pics, but if it appeared overnight then likely it isnt a hard mass.
Def go to the vet as soon as you can - and if that jaw looks worse tomorrow, you might want to consider bumping up the appointment. If its an infection, the sooner you...