Can you tell me how i can reduce pain in my left thumb?

It depends: What is the cause? Osteoarthritis is a common cause which can be treated with simple anagesics, rest, physiotherapy. There are other causes of course of thumb pain (vascuar, neurologic, orthopedic, infammatory, etc) its not an uncommon complain that a primary care physician sees. There are ot's and pt's that provide therapy, advice, splinting, ultrasound and hot parafin treatments.