The injury forced him to miss the return match between the sides at Brough Park on Sunday, and he is now resting.
But there was a further set-back when Ty Proctor sustained a neck injury in heat two of the meeting on Tyneside. And with metalwork already in his neck from a previous injury, he was taken to hospital, where he was later given the all clear.
However, it meant Berwick finished the meeting with only five riders, going down to a 47-42 defeat, with Ricky Wells top scoring on 12 and Chris Harris winning three races on his way to 11.
The previous evening, Harris raced to an impeccable 15-point maximum - his first for the club - as the Bandits achieved a comfortable 54-36 victory over Newcastle at a damp Shielfield.
In another dominant home display, all the other Bandits chipped in with at least one paid win, with reserve Jye Etheridge, on his birthday, dropping only one point from his four starts.
However, the mood was tempered by the shoulder injury sustained by Flint after tangling with team-mate Theo Pijper.
Berwick controlled the meeting from start to finish against a Newcastle side who so far this season have struggled to find any sort of consistency.
But former Bandit Lee Complin -on his comeback season in the sport - showed he still knows how to get around Shielfield as he top-scored for the Diamonds on 10 paid 12, which included two 1-5s for the visitors in heats four and 12, which prevented the home side from running away with it completely.
Paul Starke and James Wright were the only other Newcastle riders to take the chequered flag.
The Bandits now have a week off and do not race again until May 14 when they are at home against the Redcar Bears.
Meanwhile, the Bullets we’re due to be in action at Oxford last night (Wednesday) and on Saturday (May 7) they are home to Belle Vue Colts.