It's possible you may have damaged a part inside the phone or possibly lossened a cable or connection with the device on the inside. If you feel comfortable take the electronic apart, I would suggest following one of the helpful guides located here:
http://www.ifixit.com/Device/iPod_Nano_7th_Generation#guideList
If you do not feel comfortable the next best solution is to take it in for repair if you don't know anyone who may help. If you need any further assistance please feel free to ask :)
~Gadget~