What Causes Pimple On Vagina?

I have what looks like a pimple on my Vagina its not in or on the lips its like on the top where most of the hair is I've shaved like two weeks ago and when I pop it pus/blood comes out it doesn't hurt at all and I've not had sex also I haven't had a period in a year now my period is very rare should I be alert or any creams that can be adived to get