A teenager caught on CCTV punching another in Grantham Market Place pleaded guilty to a public order offence.
Alexander Stedman, 18, of Balmoral Drive, Grantham, was identifed as one of four males seen on CCTV on February 6.
Marie Stace, prosecuting, said something appeared to have been said between the defendant and the complainant, with the latter initially pushing Stedman.
However, Stedman was then seen punching the other man, and in the subsequent police interview he said he had been acting in self-defence.
He also told police that the other man had said, ‘I’m going to spill your guts out’ and this led him to think that he might have a knife, although none was seen.
Stedman, who has no previous convictions, represented himself in court and said he was ‘being stupid’.
He added that he had been drinking, and accepted that he should have walked away.
He was given a conditional discharge for 12 months, and must pay £85 prosecution costs and a £15 victim surcharge.