Suggest Treatment For Pain In Arm After An Injury

Hi, I got some injury in my bicep muscles while gymming and although the tear has healed there is still some funcitonal disorder in my arm. If I increase the weights i am using for my biceps muscles by some amount and increase the repetation i get some pain . however if i increase the weights by very small amount like 7.5kg + 1 kg , it is fine. 9 months have passed and whenever i try more repeatations with 10kg (more than 70 reps) it pains and i had to stop workout for 2 weeks n then start with 5 kg again. This was not the case prior to the injury. i was easily lifting 15kg + in my biceps workout. how to get rid of this pain?