Paraphimosis is a condition in which the skin that normally covers the penis—the foreskin—is tight when it is pulled back and then can't be returned to its normal position over the head of the penis. If not corrected, the penis will swell, and the blood flow to the head of the penis may be cut off, damaging the tissue. It's important to get medical treatment right away.
Paraphimosis can only occur when someone is uncircumcised. In infants and young children, it usually results from having the foreskin pulled back too much while cleaning the penis. In teens and adults, risk factors include having a tight foreskin, sexual activity, not putting the foreskin back in place after cleaning or urinating, and genital piercing.
Treatment may include pain control, reducing the swelling, and if necessary, surgery (including circumcision).