The foreskin on my penis doesn't come back, what are the harms? And what kind of a doctor should I consult with, to rectify this?

Phimosis. Phimosis, is a condition in males where the foreskin cannot be fully retracted over the glans penis. A urologist would be best to treat this for you. Good luck.
Foreskin. Any family physician should be able to help you with this. The solution is as simple, usually, as putting the right medication on the penis under the foreskin till the adhesions dissolve.