This little red bumps resemble acne in people and many times it is an allergic reaction to the bowls the pet eats and drinks from. If your dogs has plastic bowls I would remove them and use stainless steel, glass, or stoneware. You can clean his chin with dish detergent and water twice daily. Do not scrub as this will just cause further irritation to the skin. It may also help to contact your veterinarian to see if they have malaseb pledgets available. These are small antimicrobial wipes that will help to keep the area clean and allow it to start healing. If the condition does not improve you may want to take him to the veterinarian for antibiotics as these bumps are a sign of infection. Since it may be an allergic response I would consider trying benedryl at a dose of 1mg per pound twice daily to see if any improvement is achieved. Also, dogs who slobber a lot may be keeping the area too moist creating this irriation. It wouldn't hurt to be sure his chin is dried off a couple times a day.