Samsung flashlight stuck on and the toggle won't turn it off

usually it's some app still holding the torch, not the toggle itself. the camera is the usual suspect, or a third party flashlight app if you ever installed one. go to Settings > Apps, find Camera, Force stop, and the light normally goes off straight away. if that does nothing just restart the phone (hold side key + volume down, then Power off / Restart). if it comes back on its own after a reboot, boot into safe mode and see if it still happens there. if it doesn't, one of your downloaded apps is doing it.