See as per the guidelines of UGC, a student can't do two full time courses simultaneously. Now as you are doing Mathematics and you wish to do GNM then you have to choose one. This is not only from the perspective of UGC guidelines, but its also a concern about your curriculum as well. It may occur that your Mathematics exam as well as your GNM subjects examination can occur at the same time. That way you have to choose one/ So if you are interested in GNM then go for it and if you really enthusiastic about Mathematics Hons. then go for it. Doing both will not be beneficial or efficient at all.

To know more about Mathematics visit the link below:

https://www.careers360.com/courses/mathematics-course

To know more about GNM visit the link below:

https://www.careers360.com/courses/general-nursing-and-midwifery-course

I hope this answer helps. All the very best for your future endeavors!