If you have pain on the outside of your hip when playing butterfly guard, then try these stretches.

IT Band and Lateral Hip Stretches are important if you have pain or tightness on the outside of the hips.  These stretches and exercises are great for dealing with trochanteric bursitis (pain on the outside of the hip) as well as pain just below the outside of the knee.
Hope they help and send me any questions that you have.