Christopher Reynolds, 63, a surgeon and anaesthetist from Hartlepool, punched the victim and attacked him with a pocket knife, causing injuries, a court heard.
He pleaded guilty to assault occasioning actual bodily harm before Teesside Magistrates’ Court.
The court heard Reynolds reached for a multi-tool when the confrontation with the victim turned heated on December 20 last year.
Ian Martin, prosecuting, said Reynolds accused the victim of telling untruths about him and it developed “from words to blows”.
Mr Martin added: “During this [Reynolds] said ‘I’ve got a knife’ and it seems to have been used to cause injuries.”
Reynolds’ lawyer, Andrew Teate, said his client went over to speak to the victim who he said had been telling people that Reynolds was “making up” his military background.
Mr Teate said: “Although he put to one side these comments being made, when he saw the complainant he accepts he went over to speak to him and accepts the confrontation turned heated and he is the one who acted unlawfully.”
Mr Teate said Reynolds, who has a “proud military history”, threw the first punch and the victim retaliated and got the better of Reynolds.
He added his client is also a yachtsman and had the multi-tool with the knife on him as part of his sailing equipment.
The court heard the victim suffered two cuts to his face, described as superficial, which were treated with steri-strips.
In mitigation, Mr Teate said Reynolds, of Patterdale Street, had suffered a number of close bereavements and had been drinking too much.
He has also been diagnosed with post traumatic stress disorder and has mental health difficulties, but has sought professional help.
District Judge Steven Hood described it as a serious offence.
He told Reynolds: “Not withstanding what someone else may or may not have been saying about you or doing, it’s entirely unacceptable to be assaulting others in this way, in particular to be using a weapon like you did.”
He was sentenced to 26 weeks in prison, which was suspended for 18 months, and ordered to pay the victim £1,000 in compensation.
He will also have to wear a sobriety tag for 120 days, the maximum allowed.