Graeme Wall admitted the Summary Offences Act assault and was convicted in the Dunedin District Court in January.
The police said Mr Wall ran after the victim and assaulted him, causing pink cheeks and a hot sensation which lasted about an hour.
The incident happened about 3pm on January 30 last year, on the corner of lower Stuart St and Cumberland St. Mr Wall was fined $300 and ordered to pay court costs of $132.89.
He told the Otago Daily Times the assault amounted to holding the victim by the "scruff of the neck" because he was angry the boy and a fellow skateboarder swore at him instead of apologising.
He pleaded guilty to avoid the cost of defending the charge.
The case had already cost $3000 in legal fees.
Mr Wall said the city's skateboarding ban was not enforced, and pedestrians were at risk.
"When a little old lady gets knocked over and splits her head on the footpath, it will be an issue [then]."
Mr Wall (50), a self-employed repairman who was a cargo handler for Port Otago at the time of the incident, complained to the IPCA that the victim and his friend breached the Dunedin City Council (DCC) bylaw prohibiting skateboarding and did not receive infringement notices, and that police failed to act over the boys' offensive language.
He questioned the impartiality of a constable who helped deal with the case. The constable's son was the other skateboarder, and the constable took his son's statement about the incident. Also, the victim was the son of the police constable's partner.
Mr Wall also claimed a previous fall-out with the constable had affected the officer's objectivity.
The other officer was Senior Constable Lindsay Turner, of Port Chalmers, whom Mr Wall claimed assured him that if he was charged, the boys would be issued infringement notices for skateboarding.
In a decision issued to Mr Wall on Monday, the IPCA said the police officers' actions were "reasonable and proper".
The authority said it "would have been better" had the constable not taken his son's statement. However the constable's relationship to the boys played no part in Snr Const Turner's decision to charge Mr Wall.
The decision noted a first-time youth infringement of the skateboard ban was normally not punished.
DCC environmental health team leader Ros MacGill said the council had not issued any skateboarding ban infringement notices for at least two years.
Issuing a $50 fine for breaches was pointless, because bylaw infringers gave false names and the cost of chasing breaches was not worth it.
The council's approach to complaints was to dispatch an enforcement officer to move on the skateboarders.
The bylaw was introduced in 1995 after a pedestrian in the Octagon was injured by a skateboarder.
Dunedin police had issued four infringement notices for skateboarding in prohibited areas since the start of last year, a police spokeswoman said.
