macbook pro bottom right foot makes sound

Hey y'all,

I have an early 2011, 13' Macbook Pro. I went to take out my earbuds and to hold the computer steady, I pressed down on the right palm rest. It produced a loud-ish *pop* which startled me. It turns out that the foot on the bottom right hand corner of the laptop seems to "collapse" a bit and make said popping sun when too much force is applied. It's never done this before and none of the other feet seem to do it.

What may this indicate?

Thanks!!