I am doing 12th with pcb from nios can i apply for neet 2020?

Hello!
Yes, you can appear for neet 2020 if you have taken pcb in nios.
The qualifying exam required is 10+2 or equivalent with Physics, Chemistry, Biology/Biotechnology and English as core subject in both Classes 11 and 12 from a recognized board.
Check out the link below:
https://www.google.co.in/amp/s/medicine.careers360.com/articles/neet-eligibility-criteria

The CBSE has issued the new notice on the National Eligibility cum Entrance Test (NEET) in keeping with the recent directives issued by the Delhi High Court as per which NIOS students, Private candidates and all other aspirants who were previously ineligible, have now been allowed to apply for NEET 2019.
Neet eligibility :-Higher secondary (12 th ) or equivalent with the Physics, Chemistry, Biology/Biotechnology and English subjects, and 50% marks in the qualifying exam. Ans. The upper age of candidates applying for Neet should not exceed 25 years on the examination date (5 years' relaxation for the SC/ST/OBC candidates
Feel free to comment if you have any doubt
Good luck