I have skin rashes in the hand. My grand pa was a leprosy patient. Is it a herditery?

No. At this time we believe leprosy, also called hansen's disease, is a contageon from respiratory droplets.
Not hereditary. Leprosy is a bacterial infectious disease. It appears that there are genetic factors which may cause one to be more susceptible to infection & which impact progression of leprosy symptoms. 95% of people are immune to Mycobacterium leprae.
Not hereditary. Leprosy is not hereditary. It takes a long close contact with a patient to acquire the disease. It is very unlikely that you have it. Without seeing the rash, it is not possible to give an opinion. If the rash does not get better in 7-10 days, please consult your doctor.
RASHES ON HANDS. Don't know your age. Don't know if it itches. Don't know how long you have had it. Don't know if you are a male or female. Don't know it you take any medications. If this rash has been there for a while, you must see a dermatologist with all deliberate speed.