Because in Phemosis there is difficulty in retracting the foreskin back, there can be difficult performing sexual intercourse. It can be painful. Second, because the penis glans is not exposed, it doesn't get cleaned properly, and therfore the chances of penis skin infection are high.
Next Steps
If it is complete Phemosis, get it corrected. You must consult a general surgeon for this. For more information you can ask a direct query here on practo.
Health Tips
It can be cured.