Gary Edward Stollery, 42, was only sentenced for the assault on Monday, however has served almost the entire jail term already, after being denied bail following his arrest on April 4.

Court documents reveal Stollery and the man were once friends but have not spoken for 12 months following a fallout over the sale of a car.

The man and his son were driving on Fowlers Road at Dapto on March 27 when they saw Stollery filling up with petrol at the 7 Eleven service station and decided to pull in and speak with him.

The man didn't get out of the vehicle but wound down the passenger window and yelled through it to Stollery: "What's all this trouble for?"

Stollery's partner, sitting in the passenger seat of the couple's Ford Falcon, began screaming abuse at the man, prompting Stollery to reach into the car, grab a baseball bat and approach the man and his son with it raised in his right hand.

Stollery swung the bat at the man but it missed and hit the knee of the man's son.

The man quickly drove off and later reported the incident to police.

Officers attended Stollery's house a few days later on an unrelated matter. However, when they went to arrest him he struggled violently, threatened the officers and tried to headbutt them twice before eventually being loaded into the police paddy wagon.

In Port Kembla Court on Monday, Magistrate Michael Stoddart said Stollery would be subject to three months' supervised parole when he was released from prison next week and had to undergo any counselling sessions or treatment programs recommended by Probation and Parole officers.