I'm sorry to hear about your fall and the severe neck pain affecting your shoulders and arms. This kind of pain, especially when it worsens with certain positions like lying flat, could indicate a serious injury such as a neck strain, sprain, or possibly nerve involvement.

• It is important to avoid sleeping flat if it increases your pain; try using a supportive neck pillow or sleeping in a reclined position.
• You should seek prompt evaluation by an orthopedic specialist or a neurologist to assess the injury and rule out any nerve damage or fractures.
• Over-the-counter pain relief and muscle relaxants like cyclobenzaprine (found in medications such as Skelebenz 15 Capsule) may help reduce muscle spasms, but these should only be taken after consulting a doctor.
• If you experience worsening weakness, numbness, difficulty moving your arms, or any loss of bladder or bowel control, seek emergency care immediately.

Please arrange to see a specialist as soon as possible for a thorough examination and appropriate imaging if needed. If your symptoms worsen or you develop new neurological signs, do not delay in seeking emergency care.To narrow down potential causes, we will need some more information.Please tell me your age and gender.