Dear patient Back pain after trauma needs to be taken with care and investigated. As you have got significant trauma possibility of minor fracture needs to be ruled out. Back pain after a week might be due to muscle spasm or infection of the haematoma. Are you having fever ? If yes than abscess may be there. I would advise Xray of lumbosacral spine anteroposterior and lateral views to rule out bony abnormalities. Ultrasound of back is also advised to rule out collection. Start tab diclofenac plus serratiopeptodase combination twice a day for pain relief. Also start antibiotics. All the best.