I am not sure what may be going on with your cham, but I can give you some info on my experience.
First off I would recommend that you take him to a vet if it does not change soon. I had a similar problem where it puffed up larger than normal for a few days and then inflated really badly. I waited too long to take her to the vet because I didn't have the money at the time and it turned into a disaster! What had happened was some cricket parts had got caught up in her mouth and over time created a pocket there (from the rotting) so large that it affected her eye. I had to clean out her mouth every night till i could afford the surgery since what the vet recommended wasn't healing it. Needless to say she has only one functionable eye now. She is very strong though and still doing great! The vet said this was not a normal problem, but I just wanted to get that info out there just in case. I would hate for anyone else to have to go through what I did!