Well, you can become a teacher, preferably at a school or a coaching institute. Additionally, you may run a home tuition.

For lectureship in college/university, I'm pretty sure you might need a Masters or maybe a PhD, 'cause the competition is vast and it is a much coveted position.

Then, you may go for the research line. Get your PhDs, become a project leader in research programmes etc.

Statistician, investment analyst, accountancy and finance are some other options that you can have in your bag.
Also, being a Maths graduate gives you the option to opt for government jobs. You can apply for bank PO exams, Civil services exam, CAT, GMAT etc. The best part is, employers see maths graduates as composed, collected and committed as well as logical. So that gives you a plus in whatever job you seek out.