My father has taken personal loan of rs 100000/- from a private bank in the year 2001 after repaying till 2008 he was unable to pay due to his sickness. When he went to the bank for settlement on medical grounds and to pay final settlement amount, but bank refuse to accept. In the year 2010 he expired. Now bank is asking me to pay since I am the legal heir (son). Kindly tell guide me.

You will have to tell us where this is, It does not sound like the US or Canada, laws vary by location.

... Now bank is asking me to pay since i am the legal heir (son). Kindly tell guide me.

You need to determine if, wherever you are, there is a law requiring a child to pay the debts of his deceased father. Here in the U.S. for example, there generally are no such laws, unless the father left assets to heir(s).