How does MA handle legally owned pets that were purchased or moved from another state? Does MA's regulations say that chams cannot be owned without the proper permit? If so, get the permit! I moved to NJ with 3 exotic birds that were not on their legal pet list (which was basically only domestic poultry like chickens, pheasants, quail, or ducks). I had to show proof that the birds were legally purchased before a specific date in a state where they were legal, and get an exotic bird permit which was easy to do.
Regardless of legality, I would think any competent vet would treat an animal with such a serious problem out of compassion. I doubt they will demand to see proof of legality before treating it. This poor cham has no choice and will probably die without care.