Dear Shital ,
National Institute of Open Schooling widely known as NIOS is a central education Board established by Ministry of Human Resource Development (MHRD) and is equivalent & at Par with CBSE, ICSE and GSEB .Yes , the certificate of NIOS is valid for MBBS and Bds admission .So ,dont worry regarding your certificate is valid or not you should focus on your entrance test .
Hope it will helpful and best of luck .
Thanks
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