Unexplainable sores?

So a recent experience has taught me that even when you think you know a lot about your animal, you don't know everything. Here's the situation...my husband notices a sore on my little girl and sends me a message while I am in class that he thinks my little boy bit her. She can be annoying sometimes so I thought to myself, "She probably deserved it." When I got home I examined the sore (cause I think I am a veterinarian) and realized it was not a bit, it was an abcess. We took her the next morning to the real veterinarian and he told us that dogs have glands in their rear ends that secret really gross stuff and one of hers had gotten plugged and ruptured. The process to fix this is to clean it out, give antibiotics and possibly "express" these glands every so often. When that day comes, I will definitely be paying someone to do that for me.