Honestly get a can of WD40 with the little straw a couple paper towels and a can of spray air then spray the WD40 into the crevice around the button push it in and out a bunch of times real quick then use the spray air and clean up with the paper towels I use this process on cars all the time after people spill drinks on the center console
Besides WD-40 is very natural. If it's still stuck, you should be able to take the thing out and apart. I have taken the whole module out and saw 4 or 5 screws holding it together. All philips or allen. However, I didn't take it apart because that wasn't the reason I room it out anyways. Just be sure you take a picture of it before you take it apart, so if any buttons fall out. You'll at least have something to go by just in case.
Also, there is one screw holding the whole thing in place. To get to it, take the ash tray, or little pocket out and right behind that is a 7mm. You need not to put it back when your done though.
I wouldn't recommend WD to un-stick this button.
It might damage the finish on the control panel or harm the lens.
It sounds like maybe someone spilled something on the control head???
At any rate, your best bet is to remove the trim plate, take the control head out and disassemble the faceplate.
If you are handy with tools it should be doable.
I'd use a mild soap and water on the buttons to get any icky sticky off of them and then put it back together nice and dry. Most of the buttons will have a little "gasket" on them so watch for those.