Jake Gyllenhaal says he suffered a nasty injury while shooting the new "Road House" movie with Conor McGregor ... revealing he cut his hand right open during an intense fight scene -- and ended up with a staph infection.
The Academy Award nominee and UFC superstar opened up on working together on set during a recent episode of "Armchair Expert" with Dax Shepard ... and while they both praised each other's professionalism, there was a bit of bad blood involved.