Hey Pankaj,

If you have applied in the CW category for admission, then you will be required to present your CW certificate. If you have lost the original certificate, you must atleast be having a copy of it, you can present that. If not then, you can apply for another CW certificate and show them a proof that you have applied for the same once again. 

Above all, because this is a matter of your admission so the best option will be not to take a risk and contact the DU admission authorities immediately and directly. You may get the contacts on the official website of DU.

Hope that helps! :)