Hi

First check if the EWS criteria of your Hindi certificate is same as mentioned in the central EWS criteria ,that also depends from which state you got it issued. If it matches with central ews certificate then Your Hindi certificate is valid if and only if the concerned authorities are able to understand it, whether it's JOSAA authorities or the institute where you got enrolled because you are supposed to submit the documents there during document verification. That's the only reason JOSAA itself gives certificate format for each category. So there is no language issue for anyone concerned otherwise i don't think Hindi certificate is an issue.

Think it over.

Hope this answers your query!