Tramlining on worn roads is a common problem with wider, low profile tires such as your 225 50's. Note that this is not a Dunlop problem :-) My advice, if this was indeed a large bolt I would replace the tire! If you drive the car hard and fast with such a damaged and repaired tire you may end up with, at least, a plethora of tire belt problems, out of balance, squirming etc etc!