Broken iPhone 4 Lock Button?

I have had an iPhone 4 for about 2 years now and today, I went to unlock my phone and it seems to be stuck. I have the little touch dot on the screen in which you can control home, volume locking, etc. It's been very useful but it's driving me C R A Z Y! How much does it cost to fix it or better yet, find a free, better solution?

Same thing happened to me but i'm guessing you have go to a mobile phone repair store and just ask how much they charge and also search on youtube or something