This used to happen to the studs on the FF rear of my HZJ75 all the time, I got pretty good at getting snapped studs out.
Is there enough clearance to get a drill bit in there? If so, centerpunch, left handed drill bit (start with a smaller size first). Sometimes the left handed bit will finish extracting and it'll walk right out. Other times, just keep increasing the diameter drill bit until you can get an extractor in there.
Are there 3 of the pins in there? Might pull one of the other pins and compare to the broken stub to see if there is any threaded portion stuck in the hole - it might be just the snapped off pin. Can you drill a hole on the back side so the pin can be knocked out with a punch?