He's most likely trying to pop a hotspot. A hotspot is an area of irritated skin that is itchy and weepy and may include open sores or scabs. What starts them is usually something itchy and most often that is either fleas or allergies. Once they start, the dog will most likely keep tearing at them and keeping them from healing.
There are several possible treatments, but all have to do with wound management. Some may work better than others in specific situations, so if one doesn't seem to be working, try another.
1. keep the area clean and dry. You may have to gently wash it daily, but be sure to pat it dry afterward because moisture only encourage bacteria growth and perpetuates the problem. You might need to clip the hair away from the area to facilitate wound management. Yes, the dog will look funny for a while and it may take a long time for it to grow back since they're probably already on their winter coats by now. But it does tend to help to clip.
2. Use a cone to prevent the dog from messing with the wound.
3. Various wound treatments include:
a. hydrocortisone to stop the itching (this is the one recommended by my own vet who says it will not harm them to lick the hydrocortisone ointment)
b. antibiotic ointment such as neosporin (again, my vet says it will not harm a dog to lick this ointment)
c. use an over the counter hotspot treatment -- I've had good results with Sulfodene by Farnam
d. use Listerine -- I thought this would sting, but I tried it and my dog assured me it did not (I used vanilla mint, which is the mildest Listerine because that's what I had on hand)
I have found that for non-emergency wound management scenarios like this, that I can call my vet, describe what is going on and seek advice over the phone without having to make an appointment or take the dog in. My vet will give me a timeline for home treatment and if the dog is not better within that time limit, I take him in to see the vet. This is actually easier for the vet because he doesn't have to try to squeeze you in and the dog can start treatment immediately instead of waiting for the next available appointment. It is easier on your pocketbook, and if your dog stresses about going to the vet, then it is easier on the dog too. Not all vets will agree to do this, and most won't do it with a dog they have not personally examined within the last 12 months BUT most vets (in my experience) will do this for a regular client in this type of situation.