Display feels loose, but looks fine

I've recently noticed that when I tap on the part of my iPhone 5 display near the volume buttons, the display feels like it is bouncing up and down ever so slightly. This doesn't happen on other areas of the screen. I also looked closely at the phone but nothing looks amiss.

There's also a rattling noise when I tap on the lower left hand corner of the display. Seems to be from the camera. Or maybe it's the vibrate motor. Any ideas?

After 7 months my phone has held up pretty well overall.

 

I have a small update: I noticed that there's no display looseness at all in the morning when my phone is fairly cool or even cold from not being used.

The looseness only occurs when my phone is warm from charging or heavy use. I suspect that differences in thermal expansion between the clips and other parts are responsible. In any case, the phone doesn't appear to be having issues so I'm just going to leave the issue alone for now.