What is the treatment for a pimple like in my labia majora?

Std: A pimple on your labia majora could be caused from a variety of reasons so there is not one treatment that would be appropriate. You should see your physician or gynecologist to get a proper diagnosis and avoid sexual contact until you get treated because you may have an std (sexually transmitted disease).

Depends : Maybe simple hair follicle like ingrown hair or more complicated infection like STD. If lesion hasn't resolved in 3-5 days my recommendation is to see a doctor