HELP Pulled Leg Muscle

Hey all -

I was doing the lunges in NROLFW with weights and suddenly when I was doing a lunge with my right leg my left leg starting hurting...

Can anyone offer any advice - I was thinking I might try the foam roller to try and get any kinks that I have at the top of my leg where it feels the muscle is hurting.

I was able to change and do squats so I am a little confused at what I have done

N xx