Hi,
It could be a variety of things, like you mentioned; it could be a pimple, an ingrown hair, a small cyst, etc. ~ having a doctor examine you would be the only way to determine what it is exactly. They're common, and usually these bumps will eventually go away on their own and are mostly painless. If it continues to cause you any discomfort and the appearance worsens, you should make an appointment to have it checked out. Meanwhile, leave it alone, but keep the area dry and clean ( it may drain on it's own or dry up).
Take Care