Phimosis is a condition where the foreskin cannot be retracted (pulled back) over the glans (head) of the penis. Phimosis can cause difficulty urinating, swelling of the foreskin, and pain or discomfort during sexual activity. It can also make washing under the foreskin difficult, increasing the risk of infections such as balanitis. Phimosis can occur naturally or develop after an infection, injury or inflammation.