Set in 1960 in Bihar and based on a true story, the film is about a man who carved a path through a mountain in memory of his wife.
"It is the toughest and passionate love story. It was toughest characters of my life - both physically and mentally," said the actor here in an interview Wednesday.
Nawaz said the thought that a man carved a path through a mountain for his love and worked relentlessly for 22 years "is very tough in itself".
"And to take one's mind to that thought was very tough," added the actor.
The film also stars Tigmanshu Dhulia, Prashant Narayanan and Radhika Apte in key roles.
Nawaz will also be seen in "The Lunchbox" releasing Sep 20.