Khan agrees that the story of Malala is known to all but he is sure that few people know about her life before she was shot by the Taliban in 2012.
"This film portrays her earlier life and the spine-chilling incidents that she experienced when she was living in Swat," Khan told .
The UN had organised a "Gul Makai" screening in London about a year ago.
"It was overwhelming to see the biggies giving a standing ovation. They liked it so much that even during interval, no one left his or her seat. Each and every woman was crying.
"Even though Malala's father was watching the film for the second time, he couldn't console himself. He said 'you made our nightmares come alive again'," recalled the director.
What was Malala's reaction? "She tightened her jaws and her fists, and continuously tapped one of her feet," Khan shared.
The film is set to hit the screens on January 31. He feels it's the right time for a theatrical release.
"At present people need inspirations, especially women. This film is all about being courageous and determined during the worst situation of life. Fear is like an elastic band. You keep stretching and it keeps expanding. And this film is not only about a girl who has won the title from the UN as the most inspirational figure of decade but also a story of a father, a mother, a teacher, a soldier. Every person can relate to the story," said Khan.
But making the film wasn't an easy task.
In the beginning of the project, a Bangladeshi student who was supposed to play Malala had to back out due to security reasons. Even the director got "death threats from so many fundamental groups from Pakistan".
"I never thought of backing out. I was worried about my artistes' security on set during the shooting in Kashmir. On the first day in Kashmir, I thought of terrorist alignments with the locals but I was wrong. Kashmiri people are more patriotic than us.
"I still receive threat mails, abusive mails from unknown mail IDs," he said.
Later, he chose some interesting names from India for his film's cast.
"I wanted to cast actors who resemble the real people. But at the same time, I wanted fabulous actors to portray the characters. And casting was really lengthy but I am happy that fine actors like Atul Kulkarni, Divya Dutta are part of my film. Unfortunately, 'Gul Makai' is late Om Puri ji's last film," said Khan.
Selecting a reel Malala was most challenging for him.
"Earlier, a Bangladeshi girl named Fatima was selected for the role. But then Muslim extremists stoned and vandalised her home. She backed out. Then fortunately we got Reem Shaikh who got into Malala's skin so well that I forgot her real name and existence. She went through rigorous workshop where her accent and mannerisms got corrected," he shared.
Why didn't he go for a Pakistani actor? "At that time both the countries were going through tensed moments, and Pakistani performers were being banned from our country. I have no regrets on casting Reem though. She did her job fabulously," he said.
( With inputs from IANS )