I Injured My Thumb About 3 Weeks Ago Slap Boxing.

I injured my thumb about 3 weeks ago slap boxing. The injury is between the phalanges. there was a little pain for about 2 days and evident swelling for about 3-4 days. I thought nothing of it for about two weeks since I never lost movement and no pain during normal movements. I only experience pain while pressing down on a seatbelt. But not everything I press down on I experience pain just certain things. It's still a little swollen and tender and a little pain when I press down on the joint. I then decided to splint my thumb thinking it weren't healing cause of all the movement. I was wondering if I should still see a doctor or if i should continue using a splint. Or just let my finger free. Thanks for your answer.