Lubricant for Sticky Home Button on iPhone 5S?
It would probably be best to take your iPhone in to the Apple Store (I have had luck in the past with them replacing my iPhone when there is a hardware issue, even when I did not have an AppleCare plan for the device); however, if you are willing to risk possible (although probably unlikely) damage to the internals, you could put a small drop of rubbing alcohol on the home button and press it repeatedly until it is no longer sticky.