You can do any higher education in any branch irrespective of your bachelors degree branch. the only thing you have to keep in mind is you have to work more and hard because you have to learn all the concepts that are required for m.sc mathematics otherwise you will be lagged and it will take more time to complete the course. If you are more passionate on maths then it will be easy for you to learn the topics quickly. you can apply for the online courses to fill the gap between you and other students. I prefer learn the concepts that are mentioned in B.Sc mathematics through books or online courses and atleast get an outline of all topics so that by studying for more time and working hard you can fill the gaps of knowledge required for M.Sc mathematics and can cope up the course curriculum.

All the Best!