Radius ulnar fracture in cast near 6 weeks no pain now.but why only fingers still swell & finger join pain when touch? why fingers 1st section cant bend

Finger joint pain: Can be due to post fracture joint issues, that has nothing to do with the actual fracture , a careful followup exam and good follow up xrays may help sort this out. Often I see that in people who don't think they have arthritis but have arthritis fingers on initial X-ray, get stiff while treating the radius. The radius fractures heal but fingers stay stiff. This why early finger ROM is crucial!

Stiffness: swelling can take weeks to go away. You should go to occupational therapy to maximize your outcome and improve your stiffness

Varies: There is some degree of stones and swelling that goes along with having a firearm fracture and being immobilized in a cast. I would make sure your doctor is aware.