They could be bites, or possibly just blocked follicles, which are common in this area. They do not sound like any sort of STD. The best thing to do would be to leave them alone, apply an over-the-counter antibiotic like bacitracin or neosporin daily, and let them go away. If you keep getting new ones, show a doctor, not because they're necessarily serious but because you want to find out what they are.
Best.
Dr. Rockoff