There's nothing in the wiki about a fight at Broncos practice or Bo Nix getting injured in one. The only injury note I can find is that Bo Nix was recovering from ankle surgery this offseason (per The Fantasy Headliners). But a training camp brawl or fight-related injury isn't documented anywhere in the available sources.
If you saw this on social media or a rumor mill, it's possible it's either unsubstantiated or just hasn't been picked up by the sources the wiki tracks. As of the latest info, Bo Nix is expected to be fully healthy for camp — Fox Sports analyst Ralph Vacchiano specifically noted him being "full go" as critical to Denver's Super Bowl hopes (from the Broncos page).