This is a pattern we hear often, and it's worth explaining because it points to something interesting about how Clinical Somatics approaches pain.
The area at the base of the thumb is largely innervated from the cervical spine - typically around the C6 level. So, while the pain shows up locally, we tend to work from the centre outward rather than treating the hand in isolation. The neck, shoulder, and upper back are often part of the picture, even when nothing hurts there directly.
A few things tend to be useful in working out what's going on: whether it's one side or both, when it tends to show up, and whether specific movements - gripping, twisting, pinching - trigger it or make it worse.
If you find that different things help a little, but the pain always returns, that's often a sign the root cause sits upstream of where you're feeling it - which is exactly the kind of pattern an intro call is useful for exploring properly.