It is a disparaging thing to pay good money for the apple of one’s eye only to receive something that is less than acceptable. If you like the strop and want to give it a chance do so without invasive measures. Try laying it flat on a stable surface and rub the offensive line with your knuckle in a small circular motion in an effort to relax it to smoothness. If it looks like it is responding try the smooth side of a tea spoon in the same manner or maybe a smooth glass bottle. Then try a little snake swimming motion over the mark to work the leather. Again, don’t use so much pressure that you won’t be able to return it to the vender. If it works out you are good.
If it was not new straight out of the package I would even apply a little steam from a clean gently boiling kettle to swell or relax the crushed fibers back out. But, I think that the gentle direct rubbing will most likely smooth out the problem.
Good luck.
Regards
Chasmo