The fight between the children got out of control when he is grabbed by the throat by Aemond, who threatening to burn Luke alive just like his father, before calling Luke bastard.

Lucerys deprived the boy of an eye with the blade of a dagger, but by accident.

The children are brought to the Hall of Nine, where King Viserys angrily demands to know from how this happened. Alicent, is furious and wants to cut the boy's eye in response.

But you're protecting your son.