The incident took place at Christmas in Ylöjärvi, south-western Finland. He was also ordered to pay damages of 5,000 euros for pain and suffering, as well as mental anguish.
In addition, Nykänen was ordered to pay 3,000 euros in court costs.
Nykänen, 47, has a history of violent behaviour linked with of alcohol abuse. In 2004 he went to prison for attacking an acquaintance with a knife.
Nykänen won five World Championship gold medals and four Olympic gold medals in the mid-1980s.