Domestic abuser told his victim to lie to police and even provided excuse about tripping over a hoover
Barry Jackson also threatened to attack Danielle Hands with a machete, Hamilton Sheriff Court heard.
Jackson, 31, admitted assaulting Ms Hands at his home in Glencleland Road, Craigneuk, on November 14 last year.
He also admitted attempting to pervert the course of justice by telling the woman to shower after the attack and give police a false story.
Chloe O'Hara, prosecuting, said the couple had been together for only four weeks when the assault happened after an argument outside Jackson's house.
She told the court: "He took hold of Ms Hands by the hair and dragged her into the property.
"He then punched her on the face, causing her to fall. She tried to get up and Jackson headbutted her, knocking her to the floor again. Ms Hands tried to hit him and he threatened to attack her with a machete.
"She managed to message her father who phoned the accused to confront him.
"The accused denied anything had happened then punched his girlfriend on the face again while making more threats."
Police had been tipped off about a disturbance and officers were soon on the scene.
Ms O'Hara added: "The accused panicked and told his girlfriend to get in the shower and tell the police she had fallen over a Hoover.
"In fear she agreed and Jackson answered the door and allowed the officers entry.
"They saw Ms Hands was cut and when they asked her about this she said she had fallen over a Hoover."
The woman was taken to hospital where a cut above her eye was treated with four stitches. She also suffered bruising to her face and a cut lip.
Defence agent Ian Scott admitted Jackson's behaviour "does him no credit at all".
The solicitor added: "Both he and the complainer had been consuming drugs. He has a longstanding issue with drugs. For what it's worth, he made threats about a machete, but there was no machete present."
Sheriff John Speir deferred sentence until November 3 and Jackson, who has been in custody since his arrest, remains behind bars.