Welcome to HealthcareMagic forum.
From what I understand from your query is that you have severe pain
in the back of thigh following an injury
Well the most common cause is a muscular ache. Other cause could be subcutaneous hematoma
and even rarer is compartment syndrome
Rest and good anti-inflammatory drugs should take care of all these traumatic conditions. I suggest you to continue your current medications. Icing the affected region will be beneficial. If the pain is immense, you can get an X ray of the femur / ultrasound
soft tissues to rule out other causes.
Hope this answers your query.
Wish you a speedy recovery