Unfortunately, you cannot appear for the Joint Entrance Examination Main (JEE Main) examination to gain admission in one of the National Institutes of Technologies or NITs. NTA required that a JEE Main aspirant should complete his class XIIth exam not before than 2 years when he/she is giving the JEE Main examination.

For example, if you have passed class XII exams in 2017, then you can give JEE Main in 2017, 2018 and 2019 only, and not after that. So, according to this, you are not eligible to give JEE Main exam to get admission in NIT.

Hope I have answered your question. All the best!