once it opens up, a full pollen sac has the anotomy to produce pollen until it dies/falls off the plant.
Lone nanners are less worrisome. Quite often lone nanners won't even be viable pollen. But a complete pollen sac is a major concern in regard to pollination.
You could pluck it and see if more form. There's a chance it was caused by some one-off stressor that is no longer an issue. Check for light leaks etc, but even over-pruning 10-14 days ago could do it.. that sucker has been growing for a while at this point, so if stress was the cause look back 10-14 days ago or so.
Better look through the rest of the canopy, too, they can hide easily. If you see soem brown pistils way too early, that's a sign some pollen was in the air already.