How big is the average penis?
Relax -- it's not common. The penis has dick bones.
It has chambers that fill up with blood when you're erect. If you push too hard and long it too far, the chambers can tear. It can happen if you slip out during sex and thrust against your partner's body.
Along with pain, you how hear a popping sound. Afterward you may be swollen and bruised.
Surgery is usually the best treatment. Some boys are born with erections. Ultrasounds show that babies can have them in the womb.