My iPod is playing internal and external sound at the same time when my headphones are connected

Hi, I have an iPod nano, 16 GB, 5th gen, that I've had for almost five years. It has never given me any problems before, but today when I plugged in my headphones the sound played not only inside the headphones but through the iPod's external speaker. When I turn the volume up or down only the external sound goes up or down, the headphones still play music at the same volume. I tried connecting the iPod to other headphones, and inserted and removed the headphone jack from the iPod about 20 times, the only thing I haven't tried is restoring because I don't know if that would make any difference and I would like to avoid restoring if I can. Thank you for your time.