Lock Screen Button is Stuck!! HELP!

Today i used my iPhone 4 in the morning and it was fine. An hour later i used it and when i went to unlock it and it was stuck. It happened to a lot of my friends as well. Its very annoying to use the Assistive thing to lock my phone. The button works but only with a lot of force. I went to Verizon and they said my warranty was up last month. Will apple replace my iPhone 4 for free or not. I've heard apple is very strict with warranty. Also is there a way to fix it or no.