In general, the foreskin should move relatively freely back and forth over the glans. If your foreskin is too tight it won't move freely and will cause discomfort and avoidance of the action. For uncircumsized men, some of the most sensitive and best feelings come from the foreskin moving back and forth over the edge of the glans.

If you have tightness, you should get yourself checked by a doctor who can help determine a path that you are comfortable with that fixes the issue. Avoid circumcision except as a last resort. You will likely find that sex and masturbation is much more enjoyable when your foreskin moves freely, like it should.