Hey Sachin,
Yes, you are eligible for NIT college as the eligibility criteria for NITs /IITs/GFTIs says that the candidate must have passed with minimum 75% marks (65% for reserved category candidates) in 12th examinations  or equivalent exam or must be in the top 20 percentile in their class XII exam conducted by the respective board.
Good Luck!

Hello,

Yes if you give improvement exam of even one subject and score more than 75% or equivalent you would be eligible for getting admission in National Institute of Technology's. 

According to the recent eligibility criteria for NIT you need to score 75% or in top 20 percentile of your respective boards.