how do you update one airpod
how do you update airpod pros if only one isn’t updated
Question marked as
Leave the pods (as a pair) in their charging case, on charge and within Bluetooth range of your iPhone. The mismatch should sort itself out automatically but it shouldn't prevent you using the pods if it is delayed.
Guessing you have a mismatch because one of the AirPods has been replaced (just like I got a few weeks ago), if it has not aligned the software after a few days it might help to do a Bluetooth "forget" then re-pair your AirPods. That should remind the iPhone it has to get things sorted out.