Hello Rahul Chittur. Thanks for contacting Careers360 and we hope we will be able to answer your query.

Note that for gaining admissions into the NITs, you will need to write JEE Mains. 

For being eligible to write JEE Mains, you need to have a miminum of 75% marks in PCM. In case of ST/SC/PWD Candidates, the percentage criteria will be 65%.

I am afraid to say that as a result, you have no chance of getting into the NITs if you are a GEN category student. Hope this helps you and all the best! 

Sorry as there are no improvement exams in your board you are not eligible for nits and iits.