According to IMDB:
During the fight between Chozen and Miyagi (When Chozen is armed with the spear), Chozen strikes Miyagi on the back with the spear. This is the only time in the entire movie series someone lands a successful strike on Miyagi.
See a vintage Karate Kid toy commercial:
Produced in 1986 by Remco
Original retail price: $5.99
UPC = 050163013201