Nerve Compression in Right Arm.

I fell while riding bicycle in April 2019. I fell on my right side with my arm hitting the pavement. I started feeling mild pain in the area around deltoid and triceps muscles on the posterior side of the right arm. I ignored it because i thought it must be a small muscular injury which will dissipate on its own. It has been almost 4 months now and the pain hasn't gone away. It aggravates when i tend to stretch my right arm backwards or while doing exercise such as suryanamaskar. Also I have pain when i wake up in the morning, maybe because i tend to sleep on my right arm. The pain seems to radiate along arm and lifting weight is troublesome. I have undergone x-ray for my right arm, which was normal. I was advised to take Vitamin D3 tablets and a painkiller but that seems like a symptomatic treatment only without treating the underlying cause. I need to write a lot owing to an upcoming examination. Considering there is only a month left, I need to take urgent corrective medication