iPod nano 4th Gen 8gb earphone problem

My Apple iPod Nano 4th Gen 8gb device's earphone is having a problem. When I plug in my earphones and push them in all the way, sound only comes out of 1 earphone and not the other, but when I pull the plug out a little bit, they both work, but if I bump it, then it will go back to 1 earphone, what should I do?

(My Nano is quite old, but that is the only problem) 😠