Cover the raised area with a piece of cardboard. Lower a drift punch onto the cardboard, centering it over the highest raised point.
Hold the punch in one hand and the hammer in the other hand. Hammer the end of the drift punch lightly until you drive the nail back into the joist and the floor settles. If this does not work, you will need to remove the grout or tile.
Scrape out one side of the grout with a grout saw. This may expose the squeaky area. If not, remove the grout on the other three sides of the tile and pull the tile out of the floor.
Drill a pilot hole through the subfloor and into the joist. If you are drilling between tiles and in a grout gap, use a small enough drill bit to fit between the tiles.
Insert a wood screw into the pilot hole and drill it into place. Replace the tile. Mix grout in a bucket according to the package directions and use a grout float to apply the grout to the seams around the tile. Let the grout dry.