What's wrong with my sewing machine and how much would it cost to repair it?

While I was sewing, I heard a loud pop and then the machine sounded like it was running low on power. I turned it off and realized the needle was bent. So, I replaced the needle. But when I pushed the foot pedal the needle did not move, but I could hear the motor running. When I turn the nob on the side, the needle moves. Do you think it's a belt, or something, that broke? If you think you may know the problem, how much would it cost to fix it?