Suggest OTC Medication For Severe Pain In Shoulder And Arm Due To Pinched Nerve

I have severe pain in my left shoulder radiating down my arm, X-rays shows disc alignment in neck is off, possibly pinching on a nerve. Chiropractor seemed very concerned after no decrease in pain in 10 days and recommended MRI. Having minimal insurance, I m wondering if I should give this more time, or how critical the MRI is. What would they hope to see with this and what types of treatment would follow? Should I consider a physical therapist and would they also need the MRI? Also, what s the best over-the-counter pain medication, especially for nighttime in order to sleep. Without any pain reliever sleep is impossible.