Looks like there is a lot more rust bubbling up underneath the paint to be exposed. Most likely the whole wheel arch/door well section may have to cut out and mig welded with a new section. The structural section around the door is pretty crucial for safety to maintain structural integrity of the monocoque (assuming that is the vehicle construction) during an accident. i.e. will also stop the door popping out and the occupants being thrown into the road to be run over by other vehicles.

It maybe worthwhile getting the rest of the vehicle inspected i.e. put on a lift as well as you will probably find that the rest of the vehicle is a rust bucket as the photo is most likely showing the rust which has eaten its way through from the other side rather than from any scratched paint work.