Ditto to what everyone already chimed in with. Just to add that abscesses can actually have more than one chamber (sort of like a honeycomb) so the fact that pus came out of it doesn't mean that it's all out, and it's extremely important to get him on antibiotics because abscesses are notorious for reoccurring once the exit wound heals over.
We are as gods to the beasts of the fields. We order the time o' their birth and the time o' their death. Between times, we ha' a duty. - Terry Pratchett.
"Men have forgotten this truth", said the fox, "But you must not forget it. You become responsible, forever, for what you have tamed. - Antoine de Saint-Exupéry