Hi! I think you need consult an orthopedic for evaluation of thumb. There are many disease related to tendons in thumb. So pls go to orthopedic and get it checked for proper treatment. He might suggest you Physiotherapy depending upon your condition. If there is swelling and pain means there is an inflammation taking place which can be result of injury also.
Next Steps
consult an orthopedic for proper treatment.
Health Tips
don't move the thumb much.