I seriously doubt you have retorn anything. Are you doing bicep curls as part of physical therapy? How much weight are you using?
I had a very hard time getting back into bicep curls. If I pushed at all I would get a little tenderness where you describe. I would rest and back off completely. Then start again very, very slowly. Nothing makes you feel more like a man than doing bicep curls with 3 pound weights.

It took a while and I slowly increased the weight.
The arm behind the back is always the last movement to return and it takes a long time. I probably didn't have full, pain free, range of motion until 9 months out. And even now I still have to maintain flexiblity with stretches before I work out.