She said Southern underwent surgery at Auckland's Starship Hospital.
"They are waiting for him to get out of surgery," the friend said.
Feilding police Sergeant David Burmeister said Southern was "thrown out of the pram" but his mother escaped injury.
The driver, believed to be in her 30s, pulled over immediately in a distraught state, he said.
"There was no malicious intent and I'm pretty sure speed was not an issue," Burmeister said.
"As with everyone that drives on the road, they have to be aware of their surroundings and particularly at pedestrian crossings to prevent this sort of thing happening."
A spokeswoman at Starship said Southern was in a stable condition in the paediatric intensive care unit last night.
No charges have been laid.