It sounds like the typical look and location for a hot spot. This is a local are of bacterial skin infection that looks like the skin is melting. The treatment is usually to shave the area so that the skin is able to breathe better, antibiotics and steroids to help with the inflammation an pain. It is painful and can continue to a large area of the face and neck.
Because of the pain, your ability to clean it may be limited. I would call your vet and get an estimate for the cleaning and treatment of a hotspot...so you can know your options.
Let me know if you have further comments or questions.
Dr.V
Dr. D.A. Vamvakias
Veterinarian