Jake Andrew Severs appeared before magistrates and was also ordered to pay £200 compensation to his victim.
He must also pay £125 prosecution costs.
We previously reported that the victim was at the Mitre Hotel in Parliament Street on December 20.
He was speaking to Severs near the toilets, and was said to have known him via family connections.
The defendant was interviewed by police and handed in a prepared statement.
In it, Severs claimed he had tried to walk away from the victim, but had been pulled back.
Severs, who lives at Ballajora Hill in Maughold, was represented in court by advocate Peter Russell.
Mr Russell entered a basis of plea on behalf of his client, which was accepted by the prosecution, in which Severs said that it had been self-defence gone too far.
Severs said that he had believed he was in danger and was going to be assaulted, but accepted that his reaction was over the top.
Mr Russell asked for credit to be given for his client’s guilty plea and co-operation with the police.
A probation report said that community service was not viable as the defendant worked seven days a week, running a construction business.
Magistrates ordered Severs to pay the fine, costs, and compensation at a rate of £400 per month.