I got 31699 rank oc category in jee mains .is there any chance to get into good nit?

As the session is already over for 2017 but generally as per your rank chances should be less to get seat there in top NITs. But admission possibilities are there in colleges like Indian Institute of Information Technology, Manipur, Guru Ghasidas Vishwavidyalaya, Bilaspur, Assam University, Silchar, Gurukula Kangri Vishwavidyalaya, Haridwar etc.

To check the complete list of colleges where chances of admission are there, you can use below provided college predictor -

JEE MAIN COLLEGE PREDICTOR

Hope this helps!!!

Check it here http://www.careers360.com/collegepredictor