I’m not a healthcare practioner and would advise seeing your family doctors or ms professionals but I get the tightness down the left side of my neck and left arm & into my hand I also get ms hug both are neuropathic pain but separate. Physio & meds really help but the right pain relief med might take time to find as we are all different and it’s all a bit trial & error- take care of you ALWAYS and this helped in some kinda way at least 🍀💪👍🤞😊

Definitely tell your doctor about it but you'll find that MS tells you about all sorts of muscles that you didn't know you had. The tightness is probably a muscle spasm. I have all sorts of muscles that spasm like that on different occasions. It's a misfire in your nervous system - not sending the proper signal to that area of your body at the moment. Moving around and/or stretching that particular muscle usually gets things firing correctly again for me.