A knifeman injured a bystander's hand when tried to intervene in trouble between his current and ex girlfriend.
Craig Ditch, 29, had gone to a house in Sunderland after he found out the two women were at the same gathering because he feared there could be an argument.
Newcastle Crown Court heard when the manufacturing worker saw that a row had already started, he went into to the kitchen and asked Martin Donley why he had not stepped in to stop it.
During a confrontation that followed, Ditch picked up a bread knife, which Mr Donley reached out to grab and suffered a serious cut between his thumb and forefinger.
The 33-year-old needed four operations to repair the wound and needed time off from his job as a sheet metal worker.
He told police he was left in "limbo" waiting for it to heal so he could get back to normal life.
Ditch, of Flodden Road, Ford Estate, Sunderland, pleaded guilty to unlawful wounding.
Judge Amanda Rippon sentenced him to 12 months imprisonment, suspended for two years, with rehabilitation requirements and an order to pay £2,000 compensation.
The judge told Ditch: "You behaved aggressively and picked up a knife.
"He thought he was going to be stabbed and tried to disarm you.
"In doing that, he injured his hand and suffered nerve damage which needed four operations.
"He is a manual worker who needs his hands."
The judge said the argument between the women was "nothing to do with" Mr Donley.
Alec Burns, defending, told the court Ditch has been the victim of a stabbing in the past and lost a friend due to a knife murder so would ordinarily have a fear of such weapons.
Mr Burns said: "His girlfriend was going to see his former girlfriend, he knew there would be trouble.
"He went to see that there wasn't but got there and there already was.
"He did what he could to stop that.
"The argument was when he asked Mr Donley why he had not stopped the incident escalating."