Did he set himself up with the HondaLink app, or was he simply trying out the CarPlay/AndroidAuto feature, where his phone displays on the car's screen?
If it's HondaLink, make sure you arent using a password he knows, or if it was written down by the dealership employee somewhere. I'd change that password ASAP, since you can retrieve the car's location, remote-start, etc.. with that app.
Otherwise, if he was simply pairing his phone to the car to check out the interface, it wont really affect you, other than his phone occupying a slot in the paired devices list. You should be able to remove his phone by going into the Settings>Smartphone menu of the infotainment