Hello xAngel87x, and welcome to the forums.
I want to be sure I understand which button you're having the issue with; is it the icon (phone) for the dialer app, or is it the green call button within that app once the app is opened?
If it's the icon I'm thinking it could just be a matter of rebooting the device to clear a temporary frozen app. It could also just be a matter of putting the screen to sleep (dark) and giving the screen a good cleaning with a clean dry soft cloth.
Also, one thing you can do is go to the Android Market "Play Store" and download one of the free dialers just to make sure the system is working ok.
Let us know how it goes, and perhaps a bit more specific info as to which item is not functioning.