Braces/Retainer Question?

I was born with naturally straight teeth and have never had braces but I only have one crooked tooth on the bottom row. Its one of the middle ones, its kind of like one grew in to fast so the other one is a little crooked. But anyways, can I just get a retainer to wear at night or something to fix this? Or do I need braces? And is it possible to get braces on the backside of my teeth? I heard thats what Miley cyrus did