As you have told that your score in JEE MAINS is 24 Percentile and you belongs from OBC category and wants to seek admission in NITs. .You can't get seats in even government colleges.  To get admission into NITs one has to score minimum 95 percentile. Whether you belongs to any category.

Here is the link of College predictor by Career 360 website you can check your college according to your Rank or Percentile.

Hope you understand this very Well and All the Best !!!

Thanks and Have A Very Nice Day |||