The midfielder could have ankle damage due to the actions of Hamza Choudhury of Leicester City.
The latter went in rashly on Ritchie and could have gotten a red card in the EFL Cup tie at St. James' Park.
Not only did Newcastle lose the game, but they may be without Ritchie for the coming games.
Speaking to reporters, Bruce said: "It was difficult with the problems we had.
"I was forced to make the changes, we didn't want to do it and we've lost three tonight.
"The mess Matt Ritchie's in - it was horror challenge. When I see the mess on his leg.
"We fear ankle damage, he's got three stitches in his leg. I don't want players sent off but when it's horror challenges, it isn't good.
"It's a horror one, it's over the top. Believe me, it's a horrible one."