Well, I would sand it down to the bare metal, get a light duty mig welder or a tig welder, and weld it up in short order, then use a "soft" disk or otherwise known as a flap disk, and smooth it back out and then repaint the door skin to match.
Naturally, I would also prefer to repaint the whole car if it is a metalic color.
That's how I fixed mine on a 67 MG Midget.