Pimples can occur anywhere on the skin, include around the outside of the vagina. A pimple is simply a clogged pore, and this can happen anywhere. Sometimes, pimples around the genitals can be mistaken for sexually transmitted infections or vice versa. In particular, herpes sores start out as small blisters, and it is important to rule out herpes when you are trying to decide if this is a pimple. However, if your doctor
has already taken a close look at the area, then I think this is highly unlikely to be a sexually transmitted infection and you don't need to worry
Pimples in the vaginal area are treated the same was as pimples anywhere else - keep the skin clean and dry, and they will eventually go away on their own! In addition to pimples, another condition which is common and similar in appearance is an ingrown hair, which occurs when a hair shaft curls around and grows back down on itself, blocking the hair follicle and producing a red bump. Again, these are generally just treated with good skin hygiene but, if you find that you are getting more and more of these and you shave the pubic area, you will want to discontinue shaving, as this is a risk factor for pimples and ingrown hairs.
I recommend talking to your doctor for more specific information.