Well if i am not misinterpreting your question you mean to say you are from OBC category from rajasthan and your rank is under 1000 and you wish to know probable nit's you can get if in case i misunderstood your question pls correct me by commenting below:

with a rank under thousand you can get following NIT's

• NIT Bhopal (planning round 4)
• NIT,Allahabad (cse round 1)
• NIT , Rourkela(cse round 2)
• NIT,Tiruchapalli(electronics round 2)
• MNIT Jaipur or NIT Jaipur (cse ,architecture,mechanical, electrical,ece)

Now according to your percentile only, according to previous years analysis your rank will lie between 17k-22k best colleges you can get with this rank are 

• Netaji Subhas Institute of Technolgy,Delhi (cse , mechanical round-2)
• Delhi Technological University(environmental,chemical)

Also for more detailed analysis of which colleges you can get you can use the following toolhttps://engineering.careers360.com/jee-main-college-predictor