water line to freezer with little white plug ?

We found water on the kitchen floor and noticed that the little white plug that goes into the back of the freezer popped out and there was ice in the hole. We got the ice out, but now the little white plug won't stay in. Do we need to buy a new little white plug if so where can we buy one?
Help me please!!!!!!
patty
GE Profile 29.8 cu. ft. TFX30PR