Imogen Adams (12) was on the NX1 bus from Takapuna into the city when the driver hit the brakes hard at about 3.30pm between Esmonde and Onewa Rds.
Imogen was flung about 2m forward into the windscreen, her mum, Sarah Young-Shortt, said.
"Apparently this accident was caused by some [idiot] who thought they were entitled to cut the bus off by pulling into the bus lane," Young-Shortt wrote in a Facebook post.
Another Facebook user responded to the post, saying they were also thrown forward in the incident and left limping to work in shock and covered in cuts and bruises.
"I remember lying next to your girl, it knocked us both out from the impact," the user wrote.
Young-Shortt told Stuff that Imogen hit the windscreen so hard it cracked.
Drifting in and out of consciousness, she had no memory of the incident or her ambulance ride to Starship hospital.
She stayed overnight in hospital where she had a CT scan and x-rays.
"Thankfully nothing turned out to be fractured other than her nose," Young-Shortt told Stuff.
Imogen would take time off school as she recovered from her concussion.
Auckland Transport has been approached for comment.
