Does he just have one area like this?
Does his skin seem itchy at all?
He should be alright if you clean the area with an antibacterial soap and water, suds it up, anhd rinse it. You can do this two times a day for three days or so and it should be fine. If you see the area spread, however, then your dog may need some antibiotics to take by mouth. Usually the cases that need medications are ones that invovle a large area of the body and have many of those pimple type lesions.