I allowed my EBD to spend the night at bff house and when I went to pick him up the following day he had this huge golfball size lump on his face, very much like where your dog was bit. I went to the vet straight from her house after she told me that her 185lb dog bit him. I just about fell over and the vet said it was a puss pocket and I was so upset that she made light of it and didn't even take him to a vet ( I was at work). For that vet visit it cost me 125.00 and that was like 10 yrs ago. So definitely clean it well. Unfortunately when this happened to my dog she didn't think anything of it. She never offered to pay for it either so that was the very last time my dog was ever allowed to go to her home by himself without me. I hope all is well with your boy.