If an object weight becomes zero if it is free fall then why a person gets hurt when it falls from a height?

Weight is different from mass.

Weight is the force on a reference plane exerted by a body when acted upon by a force called gravity.

In this case since the man does not exert any force on the ground or any weighing scale (as the weighing scale would also be simulataneously falling due to gravity) his weight is zero but he do have a finite mass and hence will have a momentm change and hence he will be hurt when he falls.