If the hole is in the tread even, if it is close to the side wall, plug it. If it holds, your ahead. If it doesn't, plug it again to get you to the shop to buy a new tire.
Had tires replaced at University Volkswagen in Albuquerque, NM, about a year ago. When the mechanic diagnosed a new vibration to one of the new tires failing, I learned that the dealer doesn't provide any warranty past road hazard. All other warranty items have to be handled by the tire manufacturer. I learned my lesson and went to a local tire dealer who will stand behind what they sell for the replacement. Just saying.
