I hired an electrician to replace an illuminated bathroom medicine cabinet with a wall light fixture over a mirror (and do a bunch of other stuff). The medicine cabinet was supplied by house original (40+ yr old) NM wire running through a hole in the plaster (no box) into the top of the medicine cabinet. The new light fixture (with box) is higher and to the left of the original hole. There is a stud between the original hole and the new box.
The electrician ran the wire in front of the stud in an exposed hole, then back inside the wall to the new box. He removed some wood from the stud, but wire isn't any deeper than the back of the plaster.
I want to seal the hole even though there will be a mirror in front of it. Unfortunately he was gone before I saw his method--although drilling in the middle of the stud would have required opening up the wall. How do I fill this hole properly? If I use a spackling compound it will be pressed into the NM wire where it crosses in front of the stud. Even if that is ok, it would be bad if someone put a nail or hole there since the wire is so close to the plaster/spackling and it doesn't look like there would even be a wire there, since it is well below and to the right of the new existing light fixture.
Thanks!