That is an inflammation from the tendons within the thumb aspect from the wrist, creating pain during thumb actions or when gripping. Swelling about the thumb side of the wrist: Swelling may very well be noticeable close to the wrist joint, from time to time accompanied by fluid-loaded cysts at https://www.theorthopaedicandpainpractice.com/why-does-the-side-of-my-wrist-hurt/