is medical certificat necessary during nits document verification

I does not belong to PWD

Yes, you have to submit your medical report as mentioned in JoSAA website.

List of documents required :-
3 passport size photographs (the same as uploaded during registration)
Provisional JoSAA seat allotment letter
Photo identity card
Proof of seat acceptance fee payment
JEE Main 2017 Admit Card
Date of birth proof
JEE Main 2017 Score Card
Class XII Mark sheet
Category certificate (if applicable)

Note: If you belong to PWD category or any health related reservation you have asked for then Medical certificate would be mandatory to submit.

Good Luck!!!