You will need to have a vet clean out the pus and prescribe an antibiotic. Chameleon pus is thick and cheesy, not liquid, so antibiotics, both topical and ingested, have a hard time penetrating the pus. If it's not cleaned out, the infection can spread to the jaw bone. That's a worst case scenario, but it's horrible to see and can cause the partial or total loss of the lower jaw and death.
Jax are prone to this type of infection, and sometimes by the time the swelling appears, the infection has been present for a very long time. Luckily, it's easy to treat with a vet's help.