Mehta won the first frame quite comfortably 57-08 but thereafter completely lost his concentration as Nitesh clinched the next three frames 42-23, 34-33, 69-00.
Down 1-3, Mehta came back strongly and won the next two frames 44-35, 34-00.
In the decider, Mehta lost his rhythm completely as the 23-year-old Nitesh won the last frame comfortably by 47-0.
"It has been five years since I started playing the game and arguably this is my biggest and the best win of my career till date," Nitesh said after the match.
Also Read
Meanwhile, Sourav Kothari of PSPB won both of his games of the day against Benay Agarwal and Akram Khan (both WB) respectively.
Brijesh Damani also had a good outing as he defeated Mohit Pal 4-1.
The women's qualifiers will start tomorrow and will see Vidya Pillai, currently third ranked in world snooker rankings, in action.