The 19-year-old missed the end of his club's season with a knee injury.
As Dortmund failed to win the Bundesliga, Bellingham could only watch on the sidelines and cheer on his teammates.
Now The Mail states that his injury is serious enough that he may even need surgery.
Bellingham will not take part in Euro 2024 qualifiers against Malta and North Macedonia.
England boss Gareth Southgate may believe his side can cope without Bellingham.
While the midfielder could delay surgery, such a decision may create issues with his start of next season.