Well i would suggest to repeat JEE examination for 2020 if you are a real aspirant and want to get into IIT or NIT.It not  bad to continue your studies if you dont want to repeat the exams as there are number good instutution which provides good education system for Engineering.

40-50k rank is good enough to get into government engineering colleges.

You may apply to central universities like Silchar Uniceristy and Ambedkar Univeristy, Lucknow.

Update yourself with date for applying.

Please mention the name of the college along with your query.