Though the cut offs for different categories aren't declared yet but you got enough marks to clear JEE Main as you belong to OBC. Getting seat in nit depends upon your rank and your rank may depends upon mamy factors like number of applicants fill the form, number of applicants finally appeared in the exam, number of questions asked in the exam, difficulty level of the exam, performance of the candidate, previous year's cut offs trends but your 12th percentage doesn't play any role in calculation of your rank in JEE mains you just need to clear the minimun percentage criteria that's it. You can predict your rank with the help of jee main rank predictor and can see what nits you may get by career 360 college predictor I am providing you the link for both. 

https://engineering.careers360.com/jee-main-rank-predictor

https://engineering.careers360.com/jee-main-college-predictor

Good luck!!