Hi Aditya, it is my understanding that if the font is available in the font folder of the device, then it is accessible. What you may need to do is to make Hindi the default language of the Moodle. There are a number of other things that can void this though, for example, in a multi-language Moodle, the browser should be set to a preferred language then Moodle should be using that font.
If you want to be able to use Hindi, or even Urdu or English or whatever in a multiple language answer then that might prove a bit more tricky. There is a plugin for Atto called FontFamily, by Pau Ocaña, Sara Tellez and the Catalonia Education Department I think it is, (my Spanish is rubbish... ) which should allow you to add a Font Family to Atto. This might help or perhaps give you the essential source for modifying it for your own use. Good luck.