According to the IISER, SCB Channel has given the following criteria on it's website-

SCB Channel

1. Students who have passed 10+2 level with science stream in 2019 or 2020 are eligible to apply for admissions and appear for IAT 2020.

However, you will be considered for admissions to the degree programmes only if you obtain the cut-off marks specified for your board.

2. Students applying through SCB channel will have to appear in the IISER Aptitude Test (IAT) which will be conducted at various centres across the country.

So if you have your 10+2 from NIOS then you can be considered as NIOS is also a recognized board.