If it pulls at the hip, it's either the semimembranosus, semitendinosus, or biceps femoris long head. As alexus stated, a lacrosse ball is a good option for SMR. It appears there could be significant scar tissue and you will need to see a good therapist to locate and directly work on breaking it up.
If all you do is stretch at this point, every thing but the scar tissue will stretch. You will need to break up the adhesions, stretch, and reintegrate the new mobility. Perform SMR often and visit a therapist as often as finances allow.