A Josh Allen fan grew so angry with another customer at a Canadian McDonald's over the weekend ... he not only socked the guy in the face -- but he hurled a chair at him as well.
The wild scene happened in Truro, Nova Scotia ... after a man in a jacket and beanie got pissed with a Golden Arches employee over the toy in his Happy Meal.
Video from inside the eatery shows the guy was upset that he couldn't get Pokemon cards with his order -- and he demanded a refund.
The dude and the manager went back and forth about the situation for a while ... before the Allen fan stepped in.
The Buffalo Bills supporter seemed to want to order some food -- but when the man in the jacket had bigger desires to continue his spat over his toy ... the guys got into a verbal altercation.
"Dude," the Allen fan said. "I will knock you the f*** out."
After trading words for a few seconds, the man in Allen's No. 17 jersey eventually threw a punch ... and then a tussle ensued.
The guys locked horns for around a minute -- and at one point, the Allen fan appeared to be bitten on the forehead. When the guys eventually separated, the Bills supporter seemed to be bleeding from his eye area.
The fight, though, didn't stop there ... 'cause after they exchanged more words -- the Allen fan chucked a chair at the man -- before he took the guy's backpack and left the building.
It's unclear if police ever showed up or if any arrests were ultimately made -- we reached out to cops for comment, but so far, no word back yet.