its called a proxcimedy sensor
It's not effecting anything major, except it's blocking your phone from knowing when you're on the phone. If this doesn't matter to you and you don't mind hanging up on someone every once in a while with the side of your face, then it really doesn't matter..
Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_2_8 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8E401 Safari/6533.18.5)
Okay thanks, here's my concern. I recently put a skin on my phone(black) but since I didn't know what it was and that it was there I did not punch the hole out for it. Should I now remove it?