My right hand thumb middle part above top joint is swollen just like the index finger(same part of finger) before few months, what should i do?

See your physician: You need to clarify this by seeing your physician. This type of swelling can be joint or soft tissue. Your physician can have you see a Rheumatologist. You will need blood tests and imaging like X-ray.

Agree: Sounds like tendon swelling above the joint.Differential diagnosis trauma,dactylitis swelling of tendon which can occur with sarcoid or psoriasis.Infection or even a foreign object like a plant thorn can also cause pain.Now that this has been going on for a while I would check it out .So that you can be "all thumbs".