My thumb knuckle is enlarged, swollen, and comes out of joint due to overuse. What can I do? .

Go and check it? This means you have problem in that joint may because chronic use. Check it out with hand surgeon. Thank you.
Not sure. Your discription sounds like classic trigger thumb. Go have it checked out by your doc. This is very treatable and you will have an accurate diagnosis.
Thumb knuckle dislot. It seems you have dilocation of knuckle joint and you need to see an orthpedic doctor.Meanwhile you can take Motrin or Aleve (naproxen) if you are not allergic to these and aspirin.