A tight foreskin should always be treated under the care of a qualified medical professional.
The medical term for a foreskin that cannot be pulled back is phimosis. The medical term for a foreskin that has been pulled back but then cannot be replaced is paraphimosis.
Young boys are born with physiologic phimosis. Their foreskin stays in place naturally at first. As the natural adhesions between the inner surface of the foreskin and the head of the penis dissolve over time, boys learn to retract the foreskin and pull it forward again as they explore their genitals. Usually, they are able to do so by age 7, but some boys need more time.
Pathologic phimosis happens in teenage boys and adult men. It can be caused by a naturally tight ring at the tip of the foreskin, poor hygiene, infection, or inflammation.
Sometimes, paraphimosis occurs.  This is similar to phimosis, except the foreskin cannot be pulled forward once it has been retracted.