According to your symptoms of lower back pain, burning pain in the groins, and occasional difficulty walking in combination with the description of the pain (“like I've been punched hard…”), you could be experiencing compressive neuropathy. During nerve compression, the roots of the spinal nerves that exist the lumbar and sacral region of the spine are affected. Pressure on a nerve’s root can cause pain, itching, tingling, muscle weakness…etc. depending upon the type of nerve : either sensitive or motor nerves. If such pressure on the nerves lasts for too long, the condition can cause permanent nerve damage which manifests with numbness or muscle paralysis. Pressure on the spinal nerves is usually due to spondylotic changes (osteophytes and discus hernia) in the vertebral column. Less frequent, more rate reasons for nerve compression may include tumors, injuries, etc.

You can request an X-ray image and MRI to confirm any changes in the spinal vertebrae and to locate the exact place where nerve is pressed. Therapy for neuropathy will depend upon the diagnosis, degree of nerve damage and localisation. You can consult an orthopaedist for follow up.