Hello Aspirant,
See SC caste certificate is not sufficient for admission purpose because validity certificate is also the part of SC reservation certificate and without a validity certificate you cannot get admission. I would recommend you to contact the concerned authorities of NSIT Delhi for the same, if they can provide you some time in which you can get your validity certificate.
I hope you got it.
Good Luck!!
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile