Hello, 

To get admission into nits you don't need your jee advanced marks, you just need to score very well in jee mains. Coming to nits to get computer science in best nits you need to score more than 230 in jee mains. If you want admission in iits and to choose cse branch  you need to score rank of less than 200 to get into top 5 iits and less than 600 to get into top 8 iits.To get more information on the closing ranks, please go through the following link.

https://engineering.careers360.com/articles/iits-cutoff-for-top-btech-branches

Hope this helps....