Does a Gnome have to take a Craft or Profession skill for her obsessive trait to latch onto? In other words is he/she at 1st level forced to spend a skill rank in either Craft or Profession or can they just "let it ride" until they take one?
They technically have to choose at character creation. They will then get a +2 for any skill rolls with that skill. They do not have to spend any points on that skill at that time, or ever for that matter.