On the outside of your vagina, do you mean on your vulva? It sounds like it may be an ingrown hair, but it is hard to give you a definite answer without knowing more. It usually looks a lot like a pimple and often hurts a little when pressure is applied. These are very common, more so if you shave the area.
A quick google search and comparison with what you have going on may help to ease your anxiety. However, if it appears to be something else or is accompanied by other symptoms I would suggest seeing a doctor just to make sure everything is okay.