Hello neha,

Firstly congratulations of getting good rank in the JEE Mains.As you are not mentioned your state your from home state like your sikkim  you will get NIT sikkim computer science.It is difficult to get into top NIT(not in home state).My suggestion is go for JOSAA counseling it contains 111 institutes in that there are 23 IIT's/32 NIT's and also IIIT's .This counseling contains 6 rounds round 1 starts from oct 15 to 17.You can appear there and get good colleges Don;t miss it.

To predict your college you can use JEE Mains College predictor tool it shows Top IIT's colleges and NIT's ,IIIT's as well check below  with this link

https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer

GOOD LUCK!!!!