Hello Aspirant!
After completing your B.Sc. in Mathematics, you will get exposure to many job opportunities like -
1. RRB exams - You can prepare for Railway Recruitment Board exams for different technical and non-technical posts.
2. Banking sector - B.Sc. Mathematics graduates can apply for reputed posts like Clerk and PO by clearing IBPS and SBI exams.
3. Civil Services - You can prepare for civil service exams like SSC (CHSL/CGL), UPSC or any other state level administrative exams (for state PSC jobs) .
4. You can apply for Indian Forest Service, Indian Defence, govt. and private insurance agencies, Indian Postal Services, Income Tax Recruitment, other Accounting jobs etc.
5. You can do teaching in private/govt. schools (after qualifying B.Ed. or D.El.Ed. in addition to graduation).
6. You can join any well-known private coaching institute as a Maths Tutor.

I'll suggest you to pursue a computer course while pursuing your graduation like DCA, PGDCA, Tally, DIA or any other relevant to your field of interest. It will help you a lot from job perspective.

Hope this answer will help.