Hii.
As per your question there is no chance of getting admission to the NIT IIIT IIT or GFTIs.
The minimum criteria for boards percentage is you should score minimum 75% in PCM+ language+other subject.
You should not worry..
You can apply for state government colleges through State entrance exams and some private Colleges.
You can also prefer to take a year drop for the preparations to score good in both MAINS and boards to get good College.
All the best...

Dear Aspirant,

I am very sorry to say that there is no chance to get admission into NIT without having 75% in your 10+2 even after you scored well in your entrance and having a good rank but at the time of counseling, they will reject you.

I hope this will solve your query.

Good luck