My thought would be to drill a couple of 1/4" holes in the pushed-in section, get a 1/4" eye bolt and a maybe 4" piece of sturdy flat stock into which you drill and tap a 1/4" threaded hole. Put the eye bolt through the quarter from the outside, thread it into the flat stock on the inside, and then use a "come-along" winch to pull it out to shape. When you have it about right, weld up the holes.