My lock button is broken, what do I do?

I have the iPhone 4s which I got about 6-7 months ago. I haven't dropped it or had water damage or anything because I always take good care of my phones but all of the sudden my lock button got stuck, and isn't working. I have put on the assestivetouch option, but I still find it annoying because I'm so used to just pressing the lock button all the time. I know I could take it in to get a new phone but would I lose all of my data, like photos and such? I know that they can transfer contacts, but I wouldn't like to lose my pictures. Also I'm not sure how much warranty I have on it because when I got my phone, I wasn't really paying any attention because it's my Mom who pays attention to that. I guess I could just go in anyway… I wish I could get an iPhone 5 though because they are awesome but it isn't really necessary, I just want it. Anyway, I kind of answered my own question but if you have any suggestions please let me know, thanks. Oh! And should I go into the AT&T store or the Apple Store?

Bring it to the Apple Store or to AT&T

If you have insurance then go to AT&T if not go to apple there pretty good With customers especially under a year.

You could get a new iphone, if you back it up on iTunes it will save your data