Joshua Gardner, 33, of Westham Street, Lancaster, hurled a glass at James Taylor during a heated exchange in a nightclub.
The glass struck him in the face and caused a 3cm by 1cm wound, Preston Crown Court was told.
The incident happened at the Glow Rooms in Lancaster on December 22, 2019.
Gardner later sent messages to his girlfriend admitting his involvement.
He was arrested the following morning and made no comment in his interview, but later pleaded guilty to wounding.
Defending, William Donnelly referred to the texts and said: "One of the comments which he made was, I quote: 'I've reacted poorly', and that really is the nub of his position, that having had an exchange of words with the complainant he then reacted to a blow as he was walking away in a manner which was, to use his words, poor, and it is that which brings him before the court.
"His recollection is he threw the glass in an instantaneous reaction rather than struck him with a glass to his head."
Judge David Potter, sentencing, said: "You were punched to the back of the head by the complainant.You retaliated by turning and throwing the glass you were holding.
"You immediately regretted what you did.
"I've seen the texts you sent at 3.14am, a regret which was confirmed by way of your basis of plea.
"This was a provoked attack and your actions appear more instinctive than deliberate.
"You reacted poorly to a situation of provocation."
He was given nine months in jail, suspended for 18 months, with a rehabilitation activity and 100 hours unpaid work.
He must pay £500 compensation to Mr Taylor and £250 costs.
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