plates/screws in forearm... need ideas for arm strength

Hi all, I have a odd question, and i am not sure if anyone will be able to help me out or not, but i figured i'd ask anyways: I was in a car accident 21 years ago and had and open/compound fracture of my left radius/ulna (both forearm bones). I had 2 surgeries to repair my arm with plates/screws and subsequent physical therapy. I have MOST of my range of motion back, but not fully. I cant fully extend my hand back and when i do extend back, my fingers curl tightly. I have been doing yoga for a year now and my wrist/arm can now bear my bodyweight (w fingers curled) like in downward-facing dog, etc but my left arm is still weaker than the right and because of the weakness, i havent had much success working on pushups, etc. ... I have been trying to work on pushups more over the past month and have made some progress, but now i've been experiencing soreness/tenderness/aching in my mid forearm area where the screws are (i have a lump on one screwhead which is very tender).... Anyhoo, i'd like to know if any of you have experience with weight-bearing exercises and plates in your arm? Were you able to develop your arms? Did you work thru the pain? Is it only a temporary problem while the muscle is buiding or is it indicative of a larger problem and i should stop trying to push so much weight thru that damaged part of my body? I want to be strong and am ready to get out of the idea of being limited BUT i dont want to snap my arm!

Oh, i am also a runner / hiker so i do get upper arm/shoulder exercise from that....

thanks for any thoughts you may have on this!