Hello -
It would seem there is an infection of some sort beneath the skin, possibly an abcess related to a nearby structure -- tooth root, sinus, or blocked and infected sebacious gland. Whatever it is, it is advanced enough that it warrants medical attention. Since part of the blood supply in the facial area drains back through the same network of small veins that serve the brain, this is potentially dangerous, and undoubtedly painful.
Antibiotics are probably in order. Best to be seen at an urgent care facility if a doctor's office can't work him in promptly.
Best of luck to you both. I hope this is helpful.