The second officer took his bloodied colleague inside the hospital where doctors found his jaw was fractured in three places and his face needed 40 stitches.
He also needed to undergo reconstructive dental surgery, the spokeswoman said.
"He's pretty battered and bruised, and we're expecting him to be off work for the next couple of weeks," she said.
He was now recovering at home.
The alleged offender was arrested around 11pm and appeared at Nelson District Court today charged with aggravated wounding and male assaults female.
He was remanded in custody without plea until Friday.
"I'm in no doubt that the wider Nelson community will be disgusted by this attack," said Nelson Bays area commander, Inspector Steve Greally.
"It is completely unacceptable for an officer who is performing his duty in protecting the community to be subject to this sort of behaviour."
Police Commissioner Peter Marshall and Minister of Police Anne Tolley had expressed their concern to him over the attack, he said.
Officials figures show there were 6479 assaults on police in the three-year period ending June 30, 2012.
Last week, Roberta May Myrtle Harrison, 44, pleaded guilty to kicking and spitting on a Napier police officer who was attempting to get a breath test from her in a display of violent behaviour that was slammed as being "appalling" by a judge.
Police Association national president Greg O'Connor said attacks on officers were on the rise in a "worrying trend".
"It's hard to get statistics, because police have stopped reporting assaults in their annual report, like they used to do. But it's definitely getting worse," Mr O'Connor said.
"We all wonder why this is happening, but there is no one answer. The criminals we deal with... it's a behavioural thing."
He said attacks used to happen more often on young, less experienced officers.
But both the Nelson and Napier incidents were assaults on senior officers.
"No one is exempt now," he said.
