A few weeks ago I was riding home and my jeans got caught in the crank set. It was kind of bad, it ending up bending that metal piece that shifts the gears on the crank. (sorry, I completely forget what that thing is called) It bent it to the point where whenever it was in the third set it would make this irritating noise from rubbing on the chain and it would only shift down to set two and not to one. When I got it home, I bent it back to what I thought was normal and the noise stopped, but it still will not shift down to one. Is this something I can fix myself? Or do I need to take it to a shop?