How to deal with little holes in shower's tiled wall
Alternatives:


Remove screws and fully dry the holes and tiles there. Then back fill the holes with a colored epoxy that color matches close to the tile. 
Back fill the holes with a tile grout material of color similar to the tile color.
Break or cut out the tile with the holes and replace with one of the spare left over tiles from the original installation job. (Hoping that you have such tile).