Hello, I'm Dr. Deb and will do my best to help you today.
I'm sorry that you're having this problem with your dog. I wouldn't necessarily consider this to be an ER type of situation especially if there's not a profuse amount of blood coming from the abscess (which doesn't sound like the case at all).
My at-home treatment suggestions for such issues are as follows:
1. Gently clean the area twice a day with dilute, over the counter Betadine or Iodine (to the color of weak tea). Avoid hydrogen peroxide since it can retard healing.
2. Apply a small amount of over the counter antibiotic ointment or cream such as you would use on a wound for yourself.
3. A perfect product for this lesion would be Vetericyn Spray which may be available at local pet or grain stores. I know it can be purchase online but obviously it won't arrive in time to help your dog.
4. Preventing access to the area was a very wise move and I would keep the cone on him until he can be seen.
5. If he's not vomiting nor taking steroids or nsaid medication (and if he seems a little uncomfortable), then Aspirin can be given at a dose of 10 mgs per pound of body weight twice a day, with food to avoid stomach upset.
I hope this helps to control the situation until tomorrow. Deb