A young woman was forced to flee out of a window after her boyfriend attacked her with a martial arts weapon, Lincoln Crown Court was told.
Ashley Surfleet turned on Josina Clarke in the early hours while the couple were staying at his mother's home.
Surfleet, who had been sleeping, woke up and became angry when he noticed Miss Clarke was on the computer.
Esther Harrison, prosecuting, said: "He punched her to the face.
"He pushed and shoved her around.
"He then got some nunchucks from the bedroom and hit her repeatedly with them,'' added Miss Harrison.
''She was screaming and in pain."
Miss Harrison said the victim climbed out of a window and hid in some bushes.
Surfleet followed Miss Clarke and dragged her back into the house by the hair.
Surfleet punched her and then created a flame thrower after lighting the spray from an aerosol can which he used to burn her face.
Miss Clarke eventually managed to escape through a window and fled to a nearby house for help.
She suffered a broken arm, two black eye sand numerous cuts and bruises.
Surfleet, 20, who lives at Clinton Ville, Kirkby cum Osgodby, Market Rasen, admitted inflicting grievous bodily harm with intent on September 22, 2012.
He also admitted an earlier offence of common assault on Miss Clarke. Surfleet was sent to a young offenders' institution for three and a half years.
Judge Michael Heath told him: "You professed to love her but you treated her in a way that was completely contrary of any expression of love.
''This was a serious incident of domestic violence," the judge added.
Michael Cranmer-Brown, defending, said Surfleet has since shown genuine remorse and recognises he needs help.
He said Surfleet had been using M-Cat as well as taking prescribed drugs which caused him to behave in the way he did.