Its probably an ingrown hair.
^^ exactly what I was going to say. It's pretty common to get ingrown hairs because of shaving. Sometimes it'll be one bump, sometimes there could be 20. There are creams for the bikini zone to help with this. You could also get a professional wax or sugaring instead of shaving. Sugaring is less irritating to the skin as it only holds onto the hair ( unlike wax, it pulls on skin as well)