I had a similar thing I think when I landscaped.

Instead of mulch, some days it was gravel so you had to grip that fucking shovel like your life depended on it.

I think a couple days of that did something similar, cause my left hand would go lightly numb for weeks at a time. I think I probably had one particular “preexisting condition” of a broken bone on that side, that never really healed correctly affecting my posture

I never figured it out for sure, I just quit that fucking job when i could