Why does my white stitching look puckered after only a week of wear?

Nine times out of ten that puckering is a combination of two things: the pebble grain itself and tension that was a touch too snug. The raised texture on that leather means your stitches are actually sitting on the peaks, not in a flat plane, so when the vamp flexes with each step those peaks compress and shift, and any extra tension in the thread makes it gather up unevenly. Smooth side leather compresses flat under the thread so you never see it, but on grain like yours every stitch has a little slack or pull that shows up once the boot starts working. Don't rip anything out yet. Wear them another week or two and flex the vamp by hand a bunch. A lot of times the thread settles into the leather and the puckering relaxes down to almost nothing. If it stays bad, then you're looking at redoing that panel. For the redo, three things to change. First, back off your tension. You want the stitches snug and even but not cranked, and that different wax you mentioned was probaly telling on you without you realizing. Waxes drag differently and it's easy to pull harder to get the same feel you're used to. Second, run a groove or a light crease along the stitch line so the thread sits down into the leather instead of riding on top of the pebbling. Third, give yourself a bit more margin from the edge than you would on smooth leather, maybe an extra stitch hole's worth, becasue textured grain tears back from the edge easier when it flexes. Also worth checking your stitch spacing. If you went fairly tight to show off the white thread, that's part of the problem. Dense stitching on pebble grain bunches the surface between holes. A slightly longer stitch reads cleaner on textured stuff anyway, and the contrast thread still pops.

The white thread itself isn't the issue, so keep it. It's just less forgiving than brown because every uneven spot shows. Once the tension and spacing are right it'll look the way you wanted.

Yeah that reply about the wax dragging on you is spot on. I had almost the same thing happen on a pair of chaps I made with textured hide, used a different thread wax than usual and every stitch came out tighter without me clocking it. What fixed mine was just working the leather over my knee every night for a few days, bending it back and forth along the stitch line. The puckering eased up maybe 80 percent on its own. Never touched a single stitch. Give that a shot before you decide it needs a redo, textured grain just needs a bit of working in sometimes.

Made a satchel out of textured hide last year and hit the same wall. What helped mine was dampening the stitch line with a sponge before punching the holes. The grain compresses way better when it's slightly wet, and once it dried the thread sat down in there instead of perching on top. Haven't seen that trick mentioned yet in this thread so throwing it out there. Also I went up a thread size on the redo and it actually looked better, not worse. Thicker thread fills the holes and doesn't snap into that gathered look as easy.

Curious if you punched your holes before or after the uppers were lasted. Mine puckered worse on the panel I stitched after shaping it.

Update: turned out to be mostly the tension. Ripped out the vamp stitching and redid it with my usual brown wax, going way lighter on each pull, and the puckering is basicly gone. Didn't even need to dampen the leather, though I might try that trick on the next pair. White thread is staying.