Dear,

Minimum educational qualification for sitting in NIMCET exam is-

B.Sc. / B.Sc. (Hons) / BCA / BIT of minimum three years full-time from a recognized University with Mathematics/ Statistics as one of the subjects (candidates from open universities are also eligible)

OR

B.E./ B.Tech. from a recognized University.

So, until you have studied mathematics as one of the subject in your graduation you cannot appear in this exam.