Hi Fox,
Is the part going to be painted later, if so you can dress the skin out to try and get the damage out, be careful when dressing as you are in effect stretching the metal ever so slightly, when dressing use light blows backed up by a smotth Dollie (Bucking bar) on the damaged side, use a smooth blemish free hammer face, the blows should be in a pushing action, like your trying to smear the metal with the hammer face, you should be able to get most of the damage out, you might have to drill out a few rivets to get access to the effected area. Do you have any photo's??
As an aircraft sheet metal worker for 20yrs you learn how to work the metal with lots of practice, Good luck,
Cheers,
Nick..