You can calculate your JEE All India Rank from your percentile by using the formula:

100-your percentile * (no.of Candidates who appeared for the session)/100. And, 869010 Candidates appeared for January session. Going by that,

100-70*869010/100 = 260703 is your All India Rank. Without attaching a link of previous years cut offs, you might not have an idea of what you might have to score. But complying with your request, even with a PWD reservation, with an All India Rank of 260703, a seat in a NIT is difficult leaving alone the Best NITs. And CSE is one of the most sought out branches and so you need an All India Rank atleast less than 7000-8000. You have to appear for April session.