Hello Aspirant

Yes, it is possible for you to appear for only one subject from NIOS board and with 12th in PCB you can fill JEE mains application form.

You can appear for JEE but it will do no good for you, if you are thinking that with an marksheet of mathematics from NIOS board you will be eligible for getting admission into colleges for engineering then no it's not possible.

Your single marksheet will be considered where all of your subjects should be present.

If you don't want to waste your one year then you can reappear for all subject from NIOS Board including mathematics, then your NIOS marksheet will be considered for JEE mains eligibility while getting admission into college.

Hope this helps