This lumps needs to be examined by a veterinarian. First it needs to be identified. This will be done by having a fine needle aspirate performed--this is when a small needle is inserted into the mass to collect cells for examination under a microscope. The lump could be secondary to infection, dermal parasites, ringworm, a cyst, or dermal mass. Likely if your dog keeps scratching it open it will become infected. Also his ears need to be checked to make sure he does not have an ear infection.