Last Wednesday I fell down with my back against a wall. My lower back has been a little sore since then but 2 days ago I had extreme pain all of a suddene. It hurt so bad that I cried. The same thing happened tonight. I take ibuprofen and tramadol for pain. I also take Valium. The pain tonight was severe. It lasted about a half hour. I am using a hot pack on it right now. The pain has subsided.
Trauma to lower back may cause pain due to local muscle injury and spasm or vertebral fracture depending upon the impact force and mode.  Absence of radiating pain to lower limbs, weakness in lower limb and non involvement of urinary symptoms are pointing towards inexactness of spinal cord. My advice will be to get a X-ray of lumbosacral region to rule out any fracture.  Diclofenac with muscle relaxant and rest may be helpful. Apply local ointment also. Wishing early recover and good health.