Yep, this will probably burst open on its own and body will it bleed. It'll be very sore til it closes up but not to worry. Tight clothing can cause these and they can be large or small.
It could be acne, cists, or ingrown hair. I would ask a dr or research. Goodluck
It is likely to be a blocked sebaceous cyst.
Sometimes they do settle on their own over time. It does start to get bigger, hurt or bother you, you may need to see the doctor.
You can put a heated spoon on to the bump to help to draw it to the surface.