[OrrieG]

That big bondo patch right in front of it might be your clue. If the door got hit hard there it could have lifted the outside edge. Is the door inside jamb bent? looking from the inside can you see now deep the dent is. Cure is to figure out what caused it a reverse the force. Get the bondo out and try pulling and shrinking the depressing back out while applying pressure to the bulge. You will probably need to work the door metal perpendicular to the bulge to, time to find a third arm and hand! The lines below and above it looks pretty even with the body line so it probably did not get compressed from below.