Go straight to a Physio, do not pass go or collect £200 yadda yadda. Physio’s IME are great and much prefer their approach to Chiro’s, Osteo’s etc , but horses for courses on that one.
I had similar symptoms on my RHS a number of years ago, much much pain from between my shoulder blades, neck to shoulder and arm with numb fingers. Different causation to you but none the less, pain and numbness down the arm would suggest to me trapped or inflamed nerve – please note I’m not a physician, just experienced similar symptoms to those you are describing.
Mine turned out to be C6 & C7 prolapses. You may be more fortunate, I hope so. I am generally sorted now, although my riding position has had to change to one of more upright and so long as I do the neck retractor type exercises when I get a ‘twinge’, I can manage it all very well. I also have a physical job, so in all in, I’m delighted with my recovery from where I was. I hope this helps rather than scare to doo-diddlies out of you!!
Go well.