Given the location this would most likely be what it is - potentially it could also be something like a normally bodily wart developing.
I would dab a little neat LIQUID antiseptic on it 3 or 4 times a day for 3 or 4 days and see if it reduces in size. Often, if it is an ingrown hair, the hair has to be physically removed, or at least made to point outwards from the skin as it normally would