Hey,

As far your question is concerned as you have completed your Master's in Mathematics so to further get into research field you can go for Phd from a good Institute or research Center . You can also apply for research related jobs in few firms.

Some of them has been mentioned below,

Defense Research and Development Organization (DRDO)

Indian Space Research Organization (ISRO)

The Institute of Mathematical Sciences (IMSC)

Agricultural Statistics Research Institute

National Council for Applied Economic Research

See on their website about the eligibility criteria, if it matches with your profile you can go for it.

Hope that helps.

Thank you.