Maxi has a growth on her shoulder that started out looking like an insect bite about 5 days ago. It was just lump. 2 days ago it looked more like a rash. It was pink and had fur on it. Today it is bare, and VERY red, but it's not bloody. It's wet with puss (i think). It's still a lump and doesn't hurt or irritate her. What is it, and how can I treat this till she gets to go to the vet?