First, let me say I'm male so there may be some things I'm unfamiliar with and leaving out.
However, since you're not sexually active that pretty much rules out an STD. Pimples happen anywhere on the body, not just the face, so it's very possible it's just a zit. Zits don't always provide whiteheads right away and sometimes not at all.
Another possibility is an ingrown hair, especially if you shave.