Update--I emptied a can of Raid wasp spray into the nest in the bricks a few days ago. Didn't appear to do much at all. Today, an exterminator got a ladder (must have been called by someone else in the apartment), and just powdered/ sprayed in there. Apparently people were getting stung in the front of the building....i'm in the back. By the time that i'd noticed that there must have been a hive, i'm pretty sure it was pretty big....just sort of noticed it inadvertently.
They're all outside of the bricks/ hive, flying around trying to figure out what the hell is going on. Do they try forever to get back in to appease the queen and get at the larvae, or do they eventually move on?