Hello aspirant,
I am here for helping you.
You studied one year from any local engineering college and now you are going to take admission in NIT  firstly congratulations to you for having suscess for which you did partial drop.
If talking about gap Certificate so , answer is yes, you will have to provide gap Certificate for getting admission  in NIT so that they could know that what you did in your drop year and can verify your JEE score.
For knowing more about more you can go on the link which I am providing you below:
https://www.careers360.com/question-what-was-the-steps-that-is-to-be-taken-by-a-partial-drooper-jee-main-18
I hope it will help you...
For more queries you can upvote me and can ask in the comment box.
Best of luck.