Fishing isn't much fun when we are hurting. It's certainly possible to injure yourself trying to get that extra casting distance. A few years back I was trying for added distance and one cast the shoulder was done, almost dropped the rod in the lake. Completely tore my rotator and bicep tendon. Rotator tendon was not reparable and they had to use a cadaver tendon to replace the rotator. Everything good now. If it's still bothering you get it checked out. I waited almost a year before I finally went and had mine checked, wish I had done it sooner.