Too me, this sounds like a Hardware issue. i would say try a hard reset and if no luck, take it to your local apple store and have them have a look at it for professional advice.
But like i said, the drop has probably damaged the hardware.
If you look in the solutions or step-by-step guides, i am sure you will find a guide in repairing this issue.
If this has helped please accept the answer or score my answer.