I took a spill this weekend and noticed that where I change my gears on the left side (the three big gears) had poped out a little. Not only did it pop out but my gears are all screwy. They are not changing properly and if I switch into 2 or 3 it won't stay int. the only gear I can ride in is 1. Help!! Is it shop time or can I fix this myself easily? The 7 gears on the right seem fine.