How do I fix a sunken in lock button?

Hello everyone! My girlfriend recently came across an annoying problem with an iPod Touch I gave her. The lock button appears to have sunken in, and is now flush with the frame of the iPod. She told me that it was sticky before it finally sunk. I know how to take the front panel off the iPod, and I have tried to pry the switch out without opening it. Do I need a new switch? Or do I need to pop it open and push the switch up?

Sorry for the wall of text. Thank you!