My lock button is stuck on my iphone 4. How do I fix it?

If it´s physically stuck, schedule an appointment at the Genius bar of your local Retailstore to have it looked at.

If it´s not physically stuck but just unresponsive,

1. Try doing a hard reset:

Press and hold both the Home button and the Sleep/wake button simultaneously for about 15 seconds and release when the Apple logo appears.

2. If that doesn't work, backup the device and restore it as new.

In that case, use: http://support.apple.com/kb/HT4137

NB: set up as a NEW device because a software issue will be in the backup. If the issue persists after restoring as new, you should offer the device for service.

If you get specific error messages/codes in iTunes when updating/restoring, check this: http://support.apple.com/kb/ts3694 for causes and solutions

If you're not able to restore the device, you should use: http://support.apple.com/kb/HT1808

Using that last article will erase everything on the device, so make sure you have a backup!

Good luck

JW