Hi
Welcome to the MedHelp forum!
If there was injury to your knuckles and one of them is swollen, then it could either be due to fracture or due to reactive arthritis. It is important to get an X-ray to rule out fracture. If it is not a fracture, then rest, a dip in warm saline water, keeping hand raised on a pillow and taking an anti inflammatory analgesic will help.
Please consult an orthopedic specialist or your PCP to begin with. Hope this helps. Please let me know if there is any thing else and do keep me posted. Take care!
You may have broken something. If you don't get it checked out and it is broken, the bones may heal the wrong way and you don't want this.