If I am getting CS in Jamia Hamdard University should I take it or drop a year for NSIT or DTU?

It isn’t certain that you’ll get NSUT or DTU next year. 

Also, if you plan to join some degree program during this year drop, preparing for your entrance will become even more hectic with your college studies. Dropping a year can take a toll on your mental health as well. Moreover, It will be much more disheartening if you are unable to get into DTU or NSUT even after a drop year. 

I would personally recommend you join Jamia Hamdard University for your CS.