Usual boring advice to see a physio if possible
I wasted years in a sort of half recovered state where things were generally fine but the pain kept coming back, I sort of new it wasn’t the tendon inflamed and more bizarley it often got better with more use. I had the same thing in the other wrist as well
After years of this I slamed my bike into a tree badly crushing 2 fingers n generally shock loading my body. Sneezing was agony so off to the physio
She worked on my Thorasic joints and it helped loads
Never heard of them so googles it. Turns out the aches were tight thorasic joints. More use is better. Now I’m 100% pain free
Moral rsi is complicated and these professionals often know things we don’t
In the mean time ice and ibuprofen. Don’t do things that aggravate it. Only you will know how riding goes. Riding on the road will do better than off road.
If its on the left you don’t really need a back brake do you