Generally speaking, there will be swelling around the area of the Mohs excision. If you have any concerns you should notify your plastic surgeons office immediately.
The asymmetry is most likely a result of swelling if it's only 12 hours post-procedure. In fact, minor swelling could be present for many months. Wait a few weeks to see how things heal. Good luck!
Horizontal or oblique scars do well on the forehead, depending on whether they are in the central or lateral parts of the face. Glabellar forehead scars do better when they are vertical. I follow Langers lines for incision placement whenever possible. Best, Dr....