>>2049354
Not something I'd worry about. If it's rough you could lightly sand that area but it looks more like discoloration than anything.

>>2049369
Sounds like you're turning the preload adjustment bolt. The stem will have 1-2 bolts that pinch it around the fork's steerer tube. With the pinch bolts loose you adjust the preload bolt so that the fork isn't loose in the frame or binding up, then straighten the stem and tighten the pinch bolt(s) to the indicated torque spec.