Hi Nitish,

based on your marks in physics, chemistry and maths i can say your engineering foundation is very rudimentary. 

you can check out my similar answer here (https://www.careers360.com/question-i-have-71-in-class-12th-and-68tile-in-jee-main-what-can-i-do-next)

If you are really motivated and can study consistently for one year you can easily make it to NITs. However with your present level acads it's not realistic to aim for IITs.

I would recommend a drop year but you must be commited else there is no point wasting another year.