I mildly hurt my thumb while snowboarding three weeks ago. it still hurts and pretty swollen even with a brace. why is it still swollen?go to the doc?

Need to see ortho: If your thumb is still painful and swollen then need to rule out fracture versus ligamentous injury. Will need to see orthopedic surgeon.

Sprain or break: If you have rested, iced, and braced your thumb it might be broken if it remains swollen. I would recommend getting it xrayed especially so the appropriate treatment can be initiated and prevent future problems caused by malformations or healing inappropriately.