What Causes Pimple On Inner Labia?

Hi, I recently noticed a pimple on the inner labia.I want to know why I have it. About two weeks ago I got my papsmear results and everything was perfect. Dr. Just told me cells are swollen than normal and to go again 3 months. I wasn't on the birth control for 1 month so I dnt know if there's something wrong with hormone an that might be it. I'm only 22, mother, and have a kidney I snt know if that information helps a little