Painter and decorator Wesley Tompkinson admitted stabbing a man who he said taunted him for having a bald patch in his beard.
Tompkinson was at the Red Lion pub in Wellsway, Bath, when he believed Lee Kaylow was chanting "alopecia" at him.
After the two struggled Mr Kaylow realised he had a ripped jumper and discovered he had been stabbed in the shoulder.
Tompkinson, 27, of Edgeworth Road in Bath, pleaded guilty to wounding and possessing a knife on November 29 last year.
Judge James Patrick jailed him for 22 months.
He told Tompkinson: "Your own behaviour has affected how you can be treated.
"In many respects you are a bully and thug with a high opinion of yourself.
"You escalated the situation and did nothing to avoid it."
Neil Treharne, prosecuting, told Bristol Crown Court Mr Kaylow was with his partner at the pub and saw Tompkinson, who he knew.
Mr Kaylow stated how, suddenly, things "kicked off" and he and Tompkinson had words.
Mr Treharne said: "Mr Kaylow suggested to the defendant that they go outside.
"He then describes a scuffle but says he did not feel contact or pain.
See the crime rates in your neighbourhood, powered by In Your Area:
"He went back to his partner and said 'let's just leave'."
The court heard his partner had seen Tompkinson pull a vegetable knife from his waistband and they noticed he had a snagged jumper.
Mr Treharne said: "The defendant walked past and said 'your jumper's ripped, your a lucky man that was not in your jugular'."
Mr Kaylow went to the gents and found he had sustained a cut to his shoulder, which required three stitches at Royal United Hospital, Bath.
Catherine Spedding, defending via video link due to coronavirus lockdown, said: "Mr Tompkinson maintains he was being made fun of by Mr Kaylow.
"There is a bald patch on the right-hand side of his face and he feels self-conscious.
"He believes the victim was chanting 'alopecia'.
"He asked Mr Kaylow not to say that.
"Mr Kaylow stood up and squared up to him.
"It is agreed Mr Kaylow asked Mr Tompkinson to go outside.
"It does not excuse what happened but that's the way that the incident started."
Miss Spedding said her regretful client suffered from mental health issues and was not being medicated at the time.
