This pains happens after extensive session of masturbation. Basically it is not really because of masturbation because you can only masturbate once and then you loose erection. But if you keep your session long but not coming and by playing with it while at the same time your penis leaks semen, after some time, you begin to develop this pain in the groin. It is really temporary and not such a bad thing but the fact is you do feel the pain. You may feel hard to stand up at the time. It is only a temporary pain though which is important to discuss here because it does come from extensive session of masturbation or playing with it. Note only people have already suffered bad may experience this type of pain.