I am not a Vet tech, but I am an RN. It looks like MRSA to me. We had a lot of it in the prison where I worked and it CAN be healed with two simple Antibiotics, Bactrim Double strength (DS) and Doxcycline. Must be given 1 pill each, twice a day (per human doseages). I say this as it can show up and open and drain within only a few hours. Get the dog to the vet.