The Newcastle United player was spotted at training with a large graze on his chin, plus scrapes to his nose, hands and knee.
"The boys went out on a bike ride ... actually I wasn't there, (but) I heard about it," defender Marc Guehi told reporters on Thursday.
"I was actually talking to him, but not paying attention to him. Then he turned around and I saw that massive gash on his chin. But he's OK. It's been a bit of a joke in camp but he's doing well."
Gordon made his major tournament debut as a second-half substitute in England's 1-0 victory over Serbia in their opening group game.
Declan Rice and Kieran Trippier did not train with the main training group on Thursday morning, but left-back Luke Shaw did, raising optimism he could slot into the defence in the knockout stages.
Phil Foden remains in the UK after travelling home to be with his partner for the birth of their third child. Foden, a starter in all three of England's games, is expected to rejoin the squad before their last-16 match against Slovakia on Sunday.
