(from the interwebs...)
NFL teams are required by the league to be honest about player injuries, and failure to do so is a violation of the NFL's Personnel (Injury) Report Policy. Teams must list all players with reportable injuries, even if they are expected to play, and provide specific details. Penalties for non-compliance can include fines, suspensions, or loss of draft picks
What NFL teams must report
Any player with a reportable injury: This includes all players who have a physical injury that could affect their availability.
Specifics of the injury: Teams must be as specific as possible, including the body part (e.g., "left ankle" instead of "leg").
Injury status during practice: Even if a player practices fully, they must still be listed on the injury report if they have a reportable injury.
In-game injuries: Teams must report injuries that occur during a game as soon as the information is available.
Illnesses: A player's illness does not need to be disclosed unless it limits their participation in practice or the game.
Consequences for not being honest
Fines: The team and coaches can be fined for non-compliance.
Loss of draft picks: The league can penalize teams by taking away draft picks.
Suspensions: In severe cases, players or coaches can face suspension.