We are in the process of renovating our kitchen. Our first step was to remove one of the walls. After I ripped down all the drywall and exposed the wiring I noticed a small burn mark on the wire sheath where the wiring comes through the stud at the ceiling from the attic. The wire is for the light switch that powers the main light in the kitchen. Is this burn mark an indicatation there is a problem with the wiring or that it is unsafe. Any expertise on this situation would be greatly appreciated, thank you.