Hey, the story flows nicely and is a pleasure to read. A few points:
The ‘Nicholas was running as fast...’ paragraph needs some serious editing.

Nicholas shrugged his shoulders (redundant) and nodded his head (redundant) in agreement. -> may become ‘Nicholas shrugged, then nodded in agreement.’

I’d do away with italicizing the character’s thoughts.

“Yep, mom finally let me get them pierced last night. Pretty cool huh?” she said proudly. <- eliminate the adverb and use body language instead to convey her pride.

All the best with the story!