Any idea? How do you clean it?
You could take a small shop vac and put i up against the grill to suck out the garbage, or if you want, even better, take apart your N5 and clean it out that way with compressed air and a shop vac. Pretty simple to open up a N5 if you have the right tools:
I know it says for Iphone, but the guitar pic type tool works best on the N5:
Of you can use your fingers, this video makes me cringe but you could do it this way: