A chef hit his girlfriend so hard one of her teeth was knocked through her lower lip.
John Begg, 26, of Peter Street, Blackpool, pleaded guilty to assault.
He was bailed for pre-sentence reports by Blackpool magistrates.
Jenny Prendergast, prosecuting, said Begg went round to his ex’s Blackpool home on May 14 and there was a row about his access to their three-year-old child.
Begg grabbed her by the hair and bent her backwards.
She then felt a pain in her cheek and one of her teeth went through her lip.
Steven Townley, defending, said: “He acted entirely out of character.
“It happened because of his frustration and anger.”