Get the inflamed area rechecked asap, the cellulitis and inflamation can spread quickly and may affect his eye.
It sounds like a systemic infection along with the localized area. There should have been bloodwork done such as a white cell count to check for infection, and possibly having a blood culture done. MRSA is a possible diagnosis from his symptoms.
Encourage him to keep hydrated, fluids like pedialyte or gatorade along with soups and juices. If he's not taking in anything, he will need to be given IV fluids to help fight this infection.