I need to move a light switch to the other side of the door. I have connected the wire from the old switch to some new wire and dug a channel across the top of the door however I have had to take the wire in front of the door frame in a couple of places and then plaster over. I am worried that the wire is not set back enough in the wall in these two places and is dangerous. I am now wondering whether to chisel into the wood so I can set the wire further back into the wall or start again and take under the floor boards?? Any advice would be wonderful.

Please tell us exactly what you are trying to accomplish.

Are you trying to place the new switch on the opposite wall or are you moving the switch, across the top framing and then down the left side of the door?

You cannot have wire on the outside of the wall period.

There are two was to accomplish your goal. One is to remove small blocks of drywall from over the studs. (1) Notch the studs and then place a flat piece of metal over the notched wire to protect it from being nailed. (2) take a larger block of drywall down and with a 1/2inch wood bit, drill a hole through the stud about 2" back from the front of the stud.

Are you disconnecting the old switch from this circuit? If so, I would suggest that you would be better off removing the entire old switch loop and just run a new loop circuit from the supply to the light fixture, through the ceiling and down to the new opening.

I agree with Donf above.
If running a new switch loop isn't possible because of ceiling access I have run from the old switch location to the other side of the door by going down into the basement and up. Just be sure to not bury the splice at the original switch location. You need to leave the box and put a blank cover it.