Hi,
Where is the place where you hit the door handle? at wrist or forearm or elbow? did you have any swelling , edema after that little incident? The strength in your muscles that flexes and extend the elbow is the same like in the other limb? Does your joint feel stiffed?
How would you describe the pain? Sharp, stabbing, dull, burning?
If you touch your arm with something warm hot does it feel the same like on the other limb? or if feels more intense/less intense?
How is the skin on your affected limb? Is pale or red, or cyanotic, is your forearm warm?
How are the nails?
Did they do to you any rheumatic blood tests?


There is a condition called algoneurodystrophy which could be but.. you should be assessed for that and meanwhile you can read about it on internet.
Maybe have a check again to the doctor , to see the integrity of your nerves or if you have any rheumatic condition.

I hope I helped you somehow.

Cya