Nazeir Ahmed left the scene without alerting the emergency services or reporting what had happened outside the Brunswick Inn on Crankhall Lane, Wednesbury, to escape being breathalysed.
It was two days before he gave a voluntary interview after being traced by the police.
The 39-year-old, from West Bromwich, faced an angry backlash after his drink-fuelled pub jape of pulling down the trousers of a four-year-old child was not found funny by the other customers.
He admitted: "It was my stupidity. People started shouting and I walked out."
He drove away but returned soon afterwards - allegedly to look for a lost key that was found on the floor of his van - as Kevin Lawley, the grandfather of the young boy, dropped off a friend who lived opposite the pub and was given several different descriptions of the incident, Wolverhampton Crown Court heard.
He went to ask Ahmed, who was sitting in his Ford Transit, for his version of events and cried "oi" to catch his attention. Moments later he was felled by a blow from a wing mirror as the van reversed over his left ankle and leg which were driven over again when it went forwards and left after the defendant was told he had injured the man.
Mr Lawley suffered three fractures of the leg together with a deep laceration on his ankle which needed surgery and kept him in hospital for several days following the incident on May 11, 2018. The defendant denied causing serious injury by driving dangerously but was unanimously found guilty of the offence by the jury.
Judge Rhona Campbell dismissed the courier's claim that his vehicle had been repeatedly rammed on the car park and told the defendant: "There was no justification for you to start to reverse and you ran over him. You had drunk too much and didn't even realise you had done that.
"You did not make any call to request assistance for Mr Lawler to make sure nobody could breathalyse you and then made up a story to try to explain your behaviour."
Ahmed, from Nicholls Street, was jailed and banned from driving for four years on release from prison. Mr Lawler still has a hairline fracture to his leg and walks with a pronounced limp.