I assume you saw a doctor since you said that you tore your ligament, which I assume you mean the acromioclavicular ligament (not usually stated as ACL, anterior cruciate ligament, that's in the knee). If it's really bothering you I would go see a physical therapist as someone has already suggested to see what they recommend. Injuries of the same name can be so different
Oh by the way I'm sure a physical therapist can suggest exercises to help strengthen the area.