Took big dog out for a walk then noticed at our next walk he's walking with a limp. I can't see anything in his paw. We've been out twice since and he's still pounding around like a maniac but ocassionally lifting the weight off his back left paw. He doesn't seem to be any pain. I can't get him to sit still long enough to check inside his pads. He Gould have something in there. Any ideas? Should I take him to a vet if he's no better tomorrow?