Gosh that is some major swelling of his face. Did you see any sting marks in the swollen area when it first showed up? You can develop cellulitis from an insect bite, as I recently found out myself, which can require some heavy antibiotics. The blue tips of the comb doesn't look good. Vets can give you some much better antibiotics (Baytril) than we can get at feed stores, if that is a possibility. If not, then I would get him some Tylan 50, and either give it as a shot into the breast muscle 1/4 inch deep, or give it orally--1 ml daily for 3-5 days.