I pop a pimple near my pubic hair line. It bled a little and it went flat. Still red. Is there a way I can rule out it was an STD before going to a dr?

Probably folliculiti. S inflammation/infection of the pubic area hair follicles is frequent, especially in males or females that shave in that area. If you popped the head and there is no further drainage , it should get better by itself. If the redness continues for more than 2-3 days or its getting worse, see a doctor. You may need antibiotics.