Dear Rahul I tried that but same issue prevails. Last month changed my display for a touch screen issue. I hope the camera may have disconnected. But why the front cam symbol itself not showing on the app only I don't know.
Get it to service center.. There's nothing tat we can suggest apart from ssuggesting u to use 3rd party camera apps temporarily until it gets fixed (try to see if selfi camera opens in youcam)