How I get rid of a dot on my screen?

In the upper most part of my iPod touch, there is a grey dot. At first I thought nothing of it because I oils see everything and it was small enough to not bother me, but it has grown rather large. It is now covering my whole wifi emoticon to see if it is connected and it is almost covered up the words iPod in the upper left corner of my iPod touch. I think it may just be because it is old (I have had it for 3-4 years). Do I need to get the iPod replaced? Or just the screen? Please help!!