Besides the injury, I feel Boniface needs to try playing in other clubs first. He is a good striker that should do good and well with any other club in any other league. I still do not understand his allegiance to Bayer Leverkusen.
This is the time to be trying to leave the club for another challenge that will make him better and more proven, like Osimhen has done. Wirtz, Frimpong, and Xabi are names that will not be in Leverkusen next season, as confirmed currently; Boniface should be among them.
He had a good time last season together with the entire club. Some players don't like moving from one club to another that's why they stay in a club for a longer time. Maybe he has not also gotten a better offer from a club he likes. Next season might be better since Bayer Leverkusen will be having a new coach (Xabi Alonso will be moving to Real Madrid). A new coach could help to revitalize his career. He could also move to another club if there is an offer.