"It hit the dirt, and it was almost like a changeup back to me," Hudson said. "I reached for it and my finger got in the way and it got me right on the tip of my finger. It's a small cut right where the nail starts. It's fine. It doesn't even really hurt. We'll check it tomorrow."
Hudson had allowed one hit in 1 1/3 innings against the Cardinals. He was replaced by Brad Ziegler.
"I couldn't throw anymore," Hudson said. "I don't see any reason why I would miss more than a couple of games."
The D-backs have been careful with Hudson, who had two Tommy John surgeries, this season and it's unlikely he would have pitched on Friday anyway.
Jesse Sanchez is a national reporter for MLB.com. Follow him on Twitter @JesseSanchezMLB. This story was not subject to the approval of Major League Baseball or its clubs.