A 17-year-old Aberbargoed youth has been arrested on suspicion of aggravated burglary and grievous bodily harm.
Police have said an 18-year-old had been assaulted at a property in New Tredegar last Thursday evening.
He suffered a fractured jaw, bruising on his face and a minor stab wound in his arm.
Gwent Police said the male youth from Aberbargoed was later released on bail pending further enquiries.