In the coup attempt, after running Emperor Lee Ho through with a sword, Prince Lee Lim stabs the young Prince Lee Gon in the middle of the LEFT side of his neck with one of the pieces of Manpasikjeok (the Bamboo Flute). Later and for the rest of the show - the adult King Lee Gon has a scar by his collarbone on the RIGHT side of his neck. All the future scenes continue to show the young Lee Gon being stabbed on the Left side.
The young Prince was stabbed in the throat with the broken Flute piece on his left side but going forth the bandages and subsequent scar are on the right.
During the fight scene (10:13) the child Lee Gon is stabbed by his uncle - Lee Lim - on the left side of his neck with the now halved flute. All scenes after show his wound to be on the right side.