Rotator Cuff Burns and i cant lift weight over head without pain?

I did lat pull downs behind the back like an idiot to strengthen my weak left shoulder but it actually injured my left shoulder, i had pain for a week and then stopped. Its been almost a year now, but when i lift over head my left arm struggles like it has no strength and when doing bench its the same, with my left shoulder burning where the rotator cuff is. What should i do? Doctor would recommend Physiotherapy probably.