This sounds like garden-variety acne or minor folliculitis, which is pretty common in the genital area, buttocks, etc. Of course I can't be certain; if you're still concerned, see a health care provider.
Best wishes-- HHH, MD
I have developed a very small round, hard 'pimple' on the inside of my outer lip in my vagina. It was first noticed yesterday. I have never had this before, and there are no other symptoms. No itching, burning, unnormal discharge, fatigue, loss of appetite, NOTHING. Just a small bump that is ONLY sore IF touched, otherwise its like its not even there. Is this something I should be terribly worried about or is it simply just a pimple? PLEASE COMMENT!