1. Foreskin tear during intercourse

A tight foreskin may tear during intercourse, causing bleeding. And recurrence occurs when the next intercourse takes place. 

Circumcision is one of the option to remedy it. Or one can go for the frenuloplasty procedure, the lengthening of the frenulum.

2. "Accident" that arises from use of "machinery"

Use of vacuum cleaner or electric polishers for more sexual gratification can be dangerous.

3. Penis injury arises from sports.