There are common spray cans of wasp and hornet killer that are very effective, but you need to locate the nest entrance to spray into; perhaps that small of a nest would be soaked by the spray and the entrance isn't as critical.

I've been a party to blasting a large hive during the day, but I would have felt safer to wait until dark when the hornets are inactive; wearing raingear and running like crazy right after spraying is recommended also.