Temporal gland infection or abscess
I agree this most likely a temporal gland infection or abscess.
Usually the ones I see are due to an insect leg poking the mouth when the Cham bites down or possibly a defensive bite from the insect.
The poke injects bacteria causing infection/inflammation.
Where reptiles differ from mammals (in relation to infections), is that instead of a thin fluid pus (white blood cells) that attacks bacteria and the ruptures (like a pimple), the reptiles white blood cells form a thick cottage cheese-like barrier around the infection. Good news is the body is trying to defend itself. The bad news is it usually is not going away on its own.
To get rid of the abscess, it needs to be opened and scooped out (by a vet).
Usually this is followed by injectable antibiotics +/- Zylofen (milk enzyme solution from Zymox company- they make ear wash for dogs)
Hope that helps,
Matthew