iPhone 5 sleep/wake button not working

I've had my iPhone 5 since launch day and have had no problems up until about a week ago. It's one of my most prized possessions (along with all my other Apple products) so I've been super careful with it, and have never dropped the phone. However, the sleep/wake button is very unresponsive. It's fine when pushing on the left most side of the button, but the rest to the right is completely unresposive. Any ideas as to how I go about fixing this?

Thanks.