I was using my phone and everything was fine, and then all of a sudden, the button seemed like it needed more pressure to push, and it doesn't click back when you press it down anymore. It doesn't looks sunken, and it still works, I'm just confused? I got my phone about 4 and a half months ago, so I don't know if it's still under warranty. It works, its not like it's completely broken, but should I worry about it getting worse? I really don't know what to do 

I'm challenged when it comes to technology.