Jackson, a former Super Rugby player and Ranfurly Shield winner, was able to stay on the pitch and was stitched up after the final whistle by assistant ref Ben O'Keefe.
"I think I ran into Chris King's head and realised pretty quickly that it was in a spot that can easily swell and be cut," he told the Herald on Sunday.
"I think my biggest issue when I was playing was never putting my head into positions that I shouldn't."
He said it was first injury refereeing. The stitches would probably stay in about seven days.
"I haven't got a game next week anyway so it's worked out quite nicely to get a gash," he laughed.
Sky Sport rugby commentator Scotty "Sumo" Stevenson saw the collision and shared a picture of his mate's injury on Twitter. "It's very unusual," Stevenson said.
He said it was the first time an assistant referee had stitched up the face of the referee.
"I can guarantee it had nothing to do with any calls in the game." Stevenson said. "I saw him get tangled up and then I saw the blood. Chris King's got a pretty tough head."
Passions stirred in Dunedin as the Crusaders pipped the Highlanders 32-30. The game's outcome hinged on a video replay after Israel Dagg tackled Highlanders winger Patrick Osborne after the final hooter.
To the Dunedin crowd's heartbreak, television match official (TMO) Vinny Munro ruled Osborne grounded the ball on the touchline as he dived for what would've been a winning try.