Myositis ossificans (MO) is a rare benign pathology characterized by heterotopic bone formation within skeletal muscle, typically following trauma. Although MO is uncommon in the adductor muscle group, it may occur in athletes after direct muscular injury. We present the case of a 21-year-old male amateur football player who developed persistent groin pain after sustaining a direct blow. Initial radiographs were normal, and conservative treatment was initiated. However, the symptoms persisted over eight months. Follow-up imaging revealed a full-thickness tear of the adductor longus and mature ossification consistent with MO. Despite the presence of a palpable ossified mass, the patient declined surgical intervention and continued with conservative management. This case illustrates the diagnostic challenges of MO in atypical locations and underscores the importance of follow-up imaging in athletes with unresolved symptoms. It also raises awareness of the potential risks associated with biologic agents such as platelet-rich plasma (PRP) in the context of muscle injury.