Hi RWilliams,
If you've just finished there is hope.
If your problem is deposits of grout that are down in the crannies, get after them right now with a stiff tooth brush and water. Don't worry about your joints getting wet. That can be fixed. If you have serious grout on the tiles, you have to get it off now, or it will not come off.
If you mean you have a light haze on the tiles, leave things alone until the grout has dried a couple days. It can then be cleaned off with vinegar and water.
If you have the heavy grout in the depressions, get it out any way you can right now.