Tight foreskin us not reatked to masturbation. It is a condition by birth, and there may not be any specific reason for it. The treatment is primarily surgical correction of it. The procedure of correcting the skin is very simple and safe. The decision for a surgery is solely taken by the surgeon after physically assessing the severity. If not treated, it may predispose to frequent foreskin infection and would continue to hinder smooth sex.
Next Steps
Kindly consult with a general surgeon. For more information regarding this problem you can ask a detailed query here on practo.
Health Tips
Don't worry, it is completely curable.