"It's bruised up pretty good, but there's no break," Reid said, via BJ Kissel of the team's official website.
Reid noted after Sunday's victory that Mahomes struggled to grip the ball. Monday, the coach took it a step further, saying he changed some of the game plan in the second half due to the injury, adding more crossers and leaning on the ground game.
The adjustments showed on the field, where there were no longer deep shots against a good Patriots defense, and the offense stalled. On the Chiefs' final four drives before the end-of-game kneel-downs, the offense gained just 28 net yards and two first downs, went three-and-out three times and fumbled.
With a big lead built, the offensive lull didn't cost Reid's team against New England, but it will be something to monitor moving forward for the AFC West champs.
Sunday's victory gave K.C. a potential chance to leapfrog the Pats for a playoff bye, depending on how the final three weeks play out.