Are you able to lie down, straighten your arms, and put your upper arms close to your head while they are lying on the ground as well, without discomfort or tightness in the shoulder? If not you definitely need work on your infraspinatus.
It is amazing the control the infraspinatus exerts on the proximal end of the humerus. Some other areas you could look to is the long head tricep origin and the outer pec area.
What I recommend is using a lax ball to work these areas, I know most people that lift frequently will have adhesions in the outer pec, and almost definitely infraspinatus soft tissue issues. For awhile I had problems with my bench, it just didnt feel great, or mechanically correct. The infraspinatus and outer pec soft tissue work turned things around unbelievably. I was thinking about trying to write an article to submit to T-Mag, it is that big a difference. Whether this is what is causing your shoulder pain or not, I dont know. But I havent found many of my clients for which these techniques didnt make a drastic difference.
When kneading the infraspinatus, try working on the belly of the muscle, which lies on the shoulder blade itself. If you hit the right spot and you have issues there, you will feel a shooting pain and the whole muscle will light up. You need to work this pain out.
After you fix this issue, which I suspect you have, you will be AMAZED at the exercises that are affected by the infraspinatus. I would go as far as to say the infraspinatus effects any upper body exercise. Curls, Skullcrushers, anything… it is that vital. You will probably notice the biggest difference with bench presses, CG Bench, overhead presses, pullups and rows. Though remember, if you are dont CG or Flat Bench, there is a very good chance you have outer pec adhesions which you will need to work out to get the chest into the movement. The infraspinatus will allow for internal rotation so you can properly align your humerus with the pec muscles’ line of pull.
Now you may have injured your shoulder, and this may be too late I dont know how bad it is. But if you take it easy for awhile, the whole pain free ROM thing, and use these techniques, it should help.