Need help in 'fixing' my arm.

Note: As this is 'Off-Topic/Everything N Nothing' section i am allowed to post this thread here,atleast its not a troll thread or some other shit,i need some serious help.

Hi,i need some help with my arm because now i realized that i really have to heal/fix it,the problem is my right arm was damaged when i was like 1-2 days old (not broken bone),i was unable to even move my arm,it got a bit better after 2-3 years and i was able to use my arm a 'bit'.Now i can use it too but its hard to move it in certain directions,i can't eat or write with it so thats the reason of me being a lefty (left-handed).And the real problem is...the muscle of my right arm is smaller than the left arm,its not because of fapping! its because i barely use that arm,i lift all the weights and do all the other work with my left arm,i don't even move my right arm while walking,whenever i try to lift any weight (for long) with my right arm or do push-ups my right upper-arm really hurts.Still this arm is really precious to my because i control the cursor with my right hand and it has that amazing aim i got.I hope someone can understand & help me.