I had a chemical infection 8yrs back in my eye.now i feel something in my eye, when the lid touches to the upper/lower part in the eye. what is that ?

Adhesion?: I assume you mean a chemical burn 8 years back. Chemical burns, particularly the more severe ones, can damage the eye membrane (conjunctiva) and cause scarring. Sometimes the area of scarring and repair tissue forms adhesions (gets stuck to) a part of the covering eyelid. These develop very slowly because the eyelid moves so much. Its worth having an eye doctor take a look.

Also: In my experince, the sensation you are having now has nothing to do with the old injury. See an ophthalmolgist if you have eye pain. There are many causes, some of them very serious.