Your dog needs medical attention. Open, infected wounds can be a good breeding ground for maggots. The wound needs to be cleaned and assessed to see how much tissue damage has been done. Your dog needs antibiotics, pain medication, and needs to be prevented from licking the wound. Your dog may not be eating or drinking secondary to discomfort from the sore or the infection may have become systemic and your dog is now septic. Please seek veterinary care immediately.
Clean out the sore with some warm water then get you some anti biotic ointment like neosphen in the drug store you can find self sticking bandage and non stick gauze pads... After cleaning it out apply the ointment then place the non stick pad with med. On it then wrap it leave it on and change every day.... You might want to see a vet but try this for a couple days
You may treat minor wounds at home. You should regularly clean it with an antiseptic, Betadine is one option. The only lotion or cream I would recommend is Solugel Wound Care Gel (different to Solugel for acne treatment which contains benzoyl peroxide). You may apply a non adherent dressing over the top to protect the wound, especially if it is in an area which is susceptible to damage, however, it is important to check it daily for signs of infection. Infection is characterised by heat, swelling, pain, redness and loss of function. If there are signs of infection, the wound is deep, is causing your dog much pain or loss of function you should see your veterinarian.
That dog needs a Veterinary Doctor ASAP. Anytime a dog will not eat or drink it is serious. An infected wound is life threatening. A dog can become deathly ill very quickly, they are not as big as humans, and dehydrate quickly when ill. My prayers are with you!
Your dog may have a hot spot—this is often caused from a contact dermatitis and develops into a moist dermatitis. Hot spots become very red, inflamed, and painful.Dogs will continue to lick, knaw, and chew hot spots causing them to spread. They can become very big and infected.Take your dog to your veterinarian to make sure there is nothing else wrong—like an abscessed foreign body, laceration, or insect bite. In the time before your appointment please prevent your dog from self-mutilating the area with an Elizabethan collar, bandage, or sock—do not leave the dog unattended with sock or bandage on to make sure the dog does not chew it off and eat it.
That is pretty hard to say, because you don't know what caused this sore, and any treatment like that, might make him worse. I recommend that you take him to the vet and get him checked out. Hope this helps, good luck.
Sometimes if dogs have any types of skin disease it could have been caused by a flea or a tick or maybe his breed has a history sores...you may want to check with your dogs doctor he may know more about it and may provide a treatment for it..it can also be caused by the sun so you might definitely want to check that out by his doctor.
