There are hundreds of opportunities after B.Sc Mathematics. Please go through the following list, it may help you - 

• You can go for M.SC. or MBA, which will open new gates for you. You can become a lecturer.
• You can apply in Indian Railways for CA, TA and ticket collector
• You can go for Banking sector
• You can always go for civil services
• You can even go for private sector jobs like accountants, data entry job, software testing jobs, etc