I am not responsible if you brick/ ruin your phone in any way. If you do not know what flashing is then probably its best to get it repaired from Nokia service centre.
Choose which country version your 920 belongs(India -rm-914)
Download .ffu file for your device from here
http://www.allflashfiles.com/?s=lumia+920&submit=Search If your country variant is not available then search for Lumia 920 rm-xxx ffu download.
Download and extract wpinternals.
http://www.wpinternals.net/.php/down...-internals-1-2 Connect your device to pc.
Open wpinternals.exe and click flash.
In flash original FFU section select your location of FFU file you downloaded and click flash FFU image button