As long as the injury hasn't interferred with a joint, the scar doesn't cause any performance issues (eg. restricting flexion) and there are no long-term soundness concerns I would have no worries about a cosmetic blemish (even on the face).
Even better if the price is reduced because it is a bit ugly - handsome is as handsome does and all that.
But then my horses are primarily jumpers / eventers - if I was into showing or dressage I would probably have a different view.