Is it possible no actual 'wound' was made at all?

The 'icicle' shes uses IS similar to Edea's limit break, which when used doesn't leave permanent damage - just like all magic in the game and any other Final Fantasy game.

The large icicle, or whatever it was, is unleased at the end of your battle with Edea, when she would have low health i.e. limit break. Maybe it knocked Squall down in the same way as magic does in battle, with no physical scar. Just a theory.