Although you could use a punch to extract the nut with the bolt stub still in it, I would first try to extract the broken bolt stub with the nut still in place.
It's a small diameter bolt, so drilling and using an extractor would be tough.
Question is... how tight is the remaining bolt?
I broke a bolt and was able to manipulate the remaining stub with a pin to remove it.
Too tight for a pin? Can you Dremel a divot in the bolt in order to get a grip?
All the best
Barry