How to safely chip away at a tile to make room
You should use an abrasive grinding tool with a relatively fine grit or tooth, not a cutting tool. You don't want anything that can catch the tile and shatter it, and you want to operate at a fairly high rpm to reduce chatter and grab.
Apply pressure parallel to the face of the tile only--don't push inward or outward or you risk spalling the face of the tile. Keep the tool square with the wall.
High speed, low pressure. That's the name of the game.