Nicholas has a fascination with weapons and is always wanting to battle. Here he is fighting his dragon.
Admittedly, pairing him with a dragon was inspired by one of my all time favorite statues, Saint George (who fought the dragon) by Donatello. Seeing the statue in real life was one of those jaw drop moments for me and I still want to go stare at it again some day. (I recognize using the Saint title does make it kind of sound like Santa Claus meets Malefecent.)