You may be able to use an plate or escutcheon behind the spout.
I just finished tiling my bathroom shower/tub. Unfortunately, I just realized that I made the hole a little wider than my drain spout. So, when I screw the spout on there are places that the tile does not even reach the spout. Since I cut the hole a little too much, I am not able to put a piece of tile to cover the "spaces/holes" up. I really want to avoid caulking, so if anyone else has another idea that would be very helpful.
While it's a pain, if you have some extra tile(s), you can remove the grout around the bad one(s), then break the tile, and then install new one(s) so that it will cover the hole. As an alternative, you may be able to find a tub spout that has a larger footprint, or try to find an eschution plate you can live with.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013