Christopher Smart, 39, of Forest Road, admitted common assault when he appeared before magistrates in Mansfield on Wednesday.
The attack happened at the Stag and Pheasant pub, on Clumber Street, on October 1, while Smart was out celebrating a friend’s birthday.
Neil Hollett, prosecuting, said Smart and another man followed their victim outside and left him with small cuts near his eyes and a chunk missing from his bottom lip.
Mary Dixon, mitigating, said: “Mr Smart had been out drinking with his co-accused. He was very drunk. He was shown what he had done on CCTV and he was horrified.
“It was a very short and a very unpleasant incident. He rarely goes out and this is very much out of character for him.”
The court heard Smart was receiving sick pay after a motorbike accident and an injury at work and he continued to take painkillers and have ongoing surgery.
He told the probation service that he warned his victim not to touch his son-in-law’s partner, but he was hit on the head in the pub toilet and acted in retaliation.
His wife died after a long illness earlier in the year, the court heard.
Magistrates sentenced him to 12 weeks, suspended for 12 months, because it was a serious offence committed in drink.
They also imposed an electronically monitored curfew for 28 days, from 8pm to 10.30pm and from 12.30am to 7am, to allow him to collect his daughter from work.
He was ordered to pay £270 compensation which will be deducted from his benefits.