Smok is a very handsome boy! See what you mean about this lump. It could be an abscess, it could be a cyst, it could be a lymph node swelling due to infection, or it could be related to a dental problem. It is concerning that is has kept on swelling for the past three days, and now is the time to take him into the vet. The vet is the best person to diagnose what is causing this swelling so it can be treated appropriately. I would take Smok into the vet first thing in the morning. Good luck, I hope this helps!