Dear Aviral, we are sorry to hear that. Well, both the options sound good. We are sure you must have checked the option of supplementary exams. For now NEET has no upper age limit which means, even if you repeat a year you neednt worry about the upper age limit. Provided you meet the other eligibility criteria you can still qualify for NEET. While NTA hasnt prescribed any syllabus for NEET, CBSE syllabus covers the intrinsics of the NEET syllabus. So your 11th and 12th make more impact while preparing for NEET. Regarding NIOS, now students of Open Schools are also eligible for NEET so you can study in NIOS and not waste a year. Neverthless, if you want to pursue your Master's abroad in the future, you might not be able to because MCI diean't consider Open School Students eligible for studying abroad. So please take a call considering these facts.