AirPods Pro transparency mode not working

So I've owned AirPods pro for 10 months now since purchasing them on January 2nd of this year. However, in the past couple of months, transparency mode has completely stopped working and I'm fairly confident I know why. I noticed while shining my AirPods under a light, that the little slot on the metal band is completely full of gunk. Now, I'm terrified to stick anything in there in an attempt to clean it because it's clearly a microphone and I don't want to damage any vital components by doing so. I have tried using Blu-Tack putty, however that just pushed the gunk in further. I clean the 2 side meshes as frequently as possible so I am positive they are not the underlying issue here. Any advice would be greatly appreciated.