While eating some boiled dumplings in a box from the market, i found a piece of human hair in 1 dumpling which was in my mouth. washed the fork & ate other dumplings from the box. would this piece of hair contaminate all the dumplings & harm my body?

Little risk, nothing to worry about. For every time you notice possible contamination from fingers, hair, saliva, etc from another person -- waiters, food handlers, etc -- undoubtedly there are many more that you just didn't notice. It isn't common to acquire any significant infection from such events and hair in particular is unlikely to be contaminated with anything harmful.