Hello student if you're concerned about NIT's I'm sorry to inform you but no matter how good you score in Jee main entrance examination still you've to full fill the eligibility criteria of Jee main

Eligibility - Candidates must passed or appearing class 12 with physics chemistry physics chemistry and mathematics with minimum 75 percent marks aggregate from a recognized board. Or must be in top 20 percentile of your respective board.

So with 70 percent you're not eligible to get admission in NIT's.

Feel free to comment if you have any doubt

Good luck