I recently got a Specialized Rock Hopper from craigslist that I use mostly to ride to work. I don't know much about mountain bikes (although I'd like to know more), so I'm hoping someone can help me out without me having to go to a bike shop.

Today I took a turn wide and banged the front of my left pedal against a curb. It didn't seem to phase the bike much, but the next time I came to a stop, I felt an odd vibration in the pedals at slower speeds. It only seems to do it when I'm slowing down or speeding up but not when I'm going at a comfortable clip.

It seems like it might be the tire rubbing, but I don't see how banging the pedal could affect the tire. Additionally, the front gear won't shift from the middle sprocket (where I had it when I hit the curb). I can turn the shifter and it moves, but when I get it all the way in one direction it just makes a lot of noise like it's trying to shift, but I can't move the shifter any further.

Not a huge problem right now, but I'd like to use it for actual mountain biking when the weather warms up. It makes sense that hitting the pedal could affect the shifting mechanism, I'm just not sure how to fix it.

Is there anything anyone can think of that I might be able to do to diagnose the problem or fix the problem, or should I just take it into the shop?