Feet hurt. This is an old expression, typically associated with the South and especially concentrated around the Appalachian Mountain chain. Older usage didn't connote smelly or dirty feet, just sore feet.
There is a brand of shoe called "Hush Puppy" and it's is named that as a reference to the expression, "My dogs are barking." In the case of the shoe, Hush Puppies are supposedly so comfortable they can quiet your puppies - that is, stop your feet from hurting.
So.. this is not a phrase of american origin as suggested in the other definitions. It comes from the Cockney rhyming slang "dog meat" -> "feet" and means my feet hurt.