Hello and welcome to COL,
When I first bought Blossom my blue roan show she had a run in with a bee, On her lip, and it was all swolen and painful too, but thankfully hers was not serious and we simpy bathed it and put a bit white vinager on the sting too. It sounds like your dog has had a bad reaction and hopefully he will recover in time. Once hes well it would be nice to get a picture of the little chap on here.