Till wrote in an Instagram post Tuesday that the injury happened Monday, explaining that "while drilling I fell and straight away I knew I'd broken something."
The UFC has offered Kevin Holland the fight on short notice and Holland has agreed to it, sources told ESPN, though a final decision hasn't been made as to whether the promotion will go in that direction.
The Till-Vettori fight was scheduled to headline the second-ever UFC event on ABC.
"One thing, I know who doesn't support me in this sport and I want you to keep that same energy as the new generation say," Till's Instagram post read in part. "Mark my words I will do anything and everything to become Middleweight world champion."
Vettori (16-4-1) has won his past four fights in a row, while Holland (21-6) saw his five-fight winning streak snapped earlier this month when he lost a unanimous decision to Derek Brunson.