For essentially my whole brown and black belt life, I’ve had pretty bad tingling/numbness that radiates from my right shoulder all the way down to my right thumb and index finger. At first, I barely noticed it, only in the mornings when I used to work a “real” job and had to use the mouse with my right hand. I used to shake it off thinking it was morning numbness (is this even a thing?). It used to come and go during the day, especially when I drove with my right hand on the steering wheel. When I trained, it tended to come and go but it was never consistent.
After about 6 months of this, it became more and more frequent, and it was always worse after a hard training session. I finally brought it up casually with my physio, Jimmy from Physio Room Pymble, who did a couple of tests, and told me it might be a pinched nerve between my C6 & C7 Cervical vertebrae. I did some googling and it looks like it’s called Cervical Radiculopathy.

Looking back on how I BJJ, it’s not hard to see why I’ve had such a problem. I invert HEAPS, I get stacked often from triangles, and I use my head to post a hell of a lot. Most importantly I didn't really take any care to stop any of this from happening. This meant my neck was always subject to a lot of downward pressure, kinda like when you get stacked in double under pass (see photo above). Ten years of this definitely made a fuckery of my neck.
I briefly mentioned my issues to one of my students, Jae, who just happens to be a physio (Lively Physio Turramurra) and surprisingly, also happens to specialise in rehabilitating back injuries. He gave me a quick breakdown of what could be wrong and also explained that stretching it might actually not be such a good idea. Instead, he provided some exercises for me to do to help get me on the path to recovery, and you know what, they have actually helped tremendously. I still do these exercises on a daily basis as part of my warmup.
Three months after I started, along with some other exercises for my posture and shoulder (I’ll mention those another time), I’m now mainly pain free. The most amazing thing is that I've started training again, with a recurrence once in a while when I increase the frequency and intensity of my training. However, it’s been getting better and better when I'm consistent with the exercises.
Just remember though, I’m not a medical expert and these exercises were helpful in my case, but may not necessarily help your specific case. Basically, seek out a medical professional who knows how to deal with it or knows what they’re talking about.
Look after your bodies and good luck!