Thank you for your question. Locking of the fingers and pain located over the base is commonly symptoms of trigger finger, or in your case trigger thumb. In my consultation i would usually assess the pinpoint area of tenderness to confirm the diagnosis. There is also higher risk of getting the condition if you are female and diabetic. I would also exclude other possibilities such as arthitis which causes pain on movement but not typically locking. The pain would also be more diffuse. Once the diagnosis is confirmed, I would refer to a hand therapist for focused range of movement and some heat therapy. I would also prescribe some anti inflammatories if not contraindicated. Most of my patients would respond well to this. However in cases where the pain and locking persists, we can either attempt an injection to reduce the pain and inflammation or a release of the culprit tendon with a mini surgical incision. This usually will address the symptoms and improve the function. However please be wary that this condition can also affect the other fingers as well.