Maybe you can just use a warm compress (not hot) and apply to the area a few times a day for two days. If it disappears, then it was nothing but if it doesn't or keeps getting bigger then you should take the dog to the Vet (it could be an infection).
The green may be the pus which could indicate an infection. I'd get her checked out by the vet just to make sure. She may need antibiotics. Best wishes.