What's the best way to treat a mild muscle spasm and pain in the neck and shoulder?

you have more than a flareup;; this is now involving your nerves, so you DO need to seek medical treatment;; you may just have pulled your muscle(s) so bad that it's caused a spasm pulling along your spine, but your nerves are definitely involved;; the best thing for this is a cold pack (NOT HEAT) to your NECK to reduce the inflammation to your nerves;; then ya gotta try some upper trap stretches (really try to google this cuz pictures paint a thousand words)...best is to grab a chair & sidebend your trunk & neck in the opposite direction;; but, the massage just needs to be modified to trigger point release;; do this by poking around to the left of your cervical spine with your fingertips & trying to find little 'bubbles';; when you find this, gently press into it with your fingertips (it will hurt, then release);; then try travelling along your upper trap the same way..good luck, but this MAY give you some relief...DO NOT forget about making an appt with the doc;; radiating symptoms are not a good thing..& NEVER let something go this long before being treated..it's MUCH harder to treat because it's MUCH harder to figure out what started it in the first place;; one injury leads to a multitude to follow, esp when you don't get the right care..again, good luck!!