ANYONE KNOWS WHAT'S THIS?
A clearer pic might help - in meantime you could look up fowl pox and see if that seems to fit. When you get a better picture, post more of a description like how long it's had it, if it is eating okay, if there's any weeping/moisture/bubbling from eyes, nares, beak. Any other symptoms you notice - how is it's breathing (cough/rattle/labored?). Does the chicken free range?