M.O.
Maybe it does pinch him a bit and he doesn't have the vocabulary to say just that when you pick him up under his arms or grab him to stop him from running in the street.
I think it is normal for them to use words inappropriately simply because they don't know what else to say - maybe his legs "hurt" because they're itchy, or he's bruised, or he has a little scrape.
I would pay more attention to limping or unusual behavior than all the little comments and then he goes off running and playing. I think he's just experimenting or trying to tell you how he feels.
Try explaining to him that he needs to save the word "hurt" for bad ouchies like a cut or something that REALLY hurts him. Help him find other words for how he's feeling.