**You can often fix this without touching the glass tile**, but the remedy depends on what is protruding. The switch toggle and the thickness of the cover plate normally project; the back edge of the plate should sit against the tile.

1. **Turn off the disposal circuit at the breaker and verify that power is off** before removing the cover or adjusting the switch.
2. **If the switch sits too far forward**, check for excessive spacers or an incorrectly fitted box extender behind its metal mounting strap. Correcting those may let the cover sit against the backsplash. Don’t force it inward or overtighten screws against glass.
3. **If the electrical box itself projects beyond the tile**, an electrician needs to reposition it. Access through the wall behind it, if available, may avoid disturbing the backsplash.
4. **If tile or hardened adhesive obstructs the switch**, have the tile installer correct the opening. Chiseling installed glass mosaic can crack adjacent pieces.

A box extender generally brings a recessed box **forward**, so adding one won’t solve a switch that already sticks out. Also, don’t push the assembly arbitrarily deep: U.S. electrical rules generally limit box setback behind noncombustible tile to ¼ inch. [NFPA guidance, §314.20](https://docinfofiles.nfpa.org/files/AboutTheCodes/70/70_A2025_NEC_P08_FD_PrelimFR.pdf)

Since the backsplash is newly installed, ask the installer to return and coordinate with an electrician if the box needs moving. A photo showing the gap around the cover—and, with power verified off, the mounting beneath it—would help identify the specific fix.