Jadon Sancho was struck with an object thrown by supporters during Borussia Dortmund's meeting with rivals Schalke on Saturday.
The away side took the lead during the Revierderby, with Mario Goetze opening the scoring after 14 minutes.
During the celebrations an object, thought to be a lighter, was thrown towards Sancho from the home support, with the Dortmund forward reacting by holding his face.
The England international then left the pitch to receive treatment, with Schalke being awarded a penalty and levelling the game through Daniel Caligiuri during the time Sancho was off the field.