Yes, Sandip with your 47 marks in the OBC category you are definitely eligible for JEE Advanced examination as the cut-off for OBC category is 45 marks. So, you will need to register yourself for JEE Advanced examination which will start from 2nd May 2018 and its last date is 7th May 2018. Make sure you complete your exam registration within the timeline and give 200% in your last days' preparation before the exam which will be held on 20th May 2018.

Feel free to ask if you have any more queries. All the best!!

Sorry to say but you didn't scored enough to get seat in NIT as the cut offs for NITs for any branch is very high as compared to other colleges If we have a look on previous year cut off in general you need to score below 50k to get into NITs and below 20k to get into top NITs with you desired branch however with your obc rank you might be able to get a college but definately not any good NIT or IIIT but there are many colleges who have jee main reservations in them and some percent of seats are reserved for the students who're taking admission through mains so there's still some hope left for you. Though the cut offs aren't announced yet so need to wait for that but till than you can see what colleges you might get with this rank with the help of our jee main college predictor you just need to enter your rank your category,your home state and your desired branches and you're good to go and you can even have a look on previous year cut offs of NITs and other colleges. I am providing you the link for all. 

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

https://engineering.careers360.com/articles/jee-main-cutoff-for-top-nits

https://engineering.careers360.com/articles/jee-main-cutoff

Good Luck!!