Why does it hurt when you sit on your balls?

Answer 1

The testes are extremely delicate, and they are comfortable only in a narrow range of temperatures; if they become too hot or too cold, sperm production can be harmed. For this reason, they sit outside of the body so as to keep them cool, though they may be retracted or pulled nearer to the body should they become too cold.

They are packed densely with nerve endings. These produce a disproportionate level of sensation when stimulated.

Conveniently, the crippling pain of striking or crushing your testicles serves as a reminder not to strike or crush them - after all, the future of the human race depends upon their health and continued function.

Answer 2

This are valueable organs that are very fragile. When someone squeezes them, it is crushing the organs (testicles). The testicles hang to keep cool in a flap of skin right below the penis. Also, there is a major artery connecting the testicles to another part of your body lofted in the upper chest. Sometimes, when your testicles are squeezed you feel the pain go up in a straight line up your body. If they are squeezed hard enough, it's could result in stomach pain and vomiting.