Hii!
Firstly, you can apply for class 12th via NIOS. NIOS is a reknowned and recognised Board of education and all the certificates you get from there are valid in maximum fields. So, you can apply for any of the exams thereafter.
Secondly, both science and commerce streams are good in their own ways. You get ample of job opportunities after completing your course via any of the two Subjects.
If you are good in maths, you can go for fields such as Engineering and architecture, Defence, Research  etc., Via Science.
You can go for jobs such as Banking, accountancy, statistics, management etc., Via Commerce.
So, the decision depends on you.
Hope this helps.
Good luck!