Kevin Kibble launched the assault at the Walker Tavern in Cupar, Fife, on March 3 last year.
Cupar Sheriff Court heard Kibble's victim had to have reconstructive surgery, with cartilage taken from another part of his body to rebuild the damaged lobe.
Now Kibble faces a jail term after he admitting assaulting the man to his severe injury and permanent disfigurement.
Kibble, of Tarvit Terrace, Springfield, Fife, admitted a charge on indictment over the incident in the town's The Cross last year.
An allegation he repeatedly attempted to butt the man causing him to fall to the ground was removed.
Defence solicitor Douglas Williams said: "The accused had a bad record in his adolescence but has found a stable job. He is working as a steel erector and welder."
Sheriff Brian Cameron deferred sentence.