Police searched Thomson's home on November 2 and found a cannabis-growing room and 200g of cannabis plant material, commonly known as "cabbage".
Lawyer Whare Hika told Judge Thomas Ingram that his client insisted he was acting in self-defence as he believed his family in the car were in danger.
Thomson outlined his remorse for his actions in a letter of apology handed to the judge, Hika said.
Judge Ingram told Thomson, who he noted had several convictions for violence, that he failed to understand the seriousness of the situation by trying to excuse his behaviour.
"You and anybody else out there needs to understand people who engage in this type of offending go to jail," the judge said.
"Nothing other than a sentence of imprisonment is appropriate, particularly given this violence was clearly premeditated."
Thomson wept as he was taken away to start serving his prison sentence.