Hreflang Tags For Localised Version of the Website

What If there is a website which creates content in English as well as Hindi Language. PS: the content, URL & Title is unique on both the pages & Hindi is a subdomain to the main website. Will there be a need of putting hreflang tag on the both the pages? Currently if the hreflang tag is included, Google thinks that the Hindi article is a version of English article and only shows one of the content piece according to the user preference or region?

What are your comments on this?