If the puncture is in the tread section of the tire and is small enough, the tire can usually be repaired.
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=77
But, if the puncture is large enough, the tire might not be able to be repaired.
I once had a co-worker ask me why his Prius made a clunking noise each time the tire rotated.
I removed the tire and found a 3/8" dia x 3" long lag bolt stuck in the tread of the tire.
So each time the tire rotated, the bolt got pushed up into the wheel causing the clunking noise.
It took an impact gun to remove the lag bolt.
And the tire had to be replaced.
Tester