If that is an active nest there will be a hornet standing guard at the entrance. At this time of year I don't think you have anything to worry about.
I have a lawn maintenance business. I deal with them constantly. I've gotten rid of quite a few of them in the past. Here's what you do;
Place a garbage can directly under the nest. Keep the lid handy. Use a flat shovel. In one quick precise motion, shave it from the underside of your deck. When it falls into the garbage can, drop the shovel and grab the lid and cover the can. Do what you want with them after that.
Bald faced hornets are good pollinators, but later in the season when there are fewer blossoms, they become pests looking for whatever they can find. The can ruin an outdoor event. The are persistent but rarely a threat. Get close to their nest and that is a different story. They are fiercely defensive. In the fall, they will all leave the nest and find a place to winter over and look for a place to start a nest of their own in the spring If they survive.
A little known fact. All the hornets in the nest are sisters.