Hitting a nerve is possible since the sciatic nerve runs in this general area. You may not have hit the nerve directly but the depot may be pressing against it. I have had similiar symptoms as you describe (though I do not have gyno). IM inject into the quad, later felt slight pain under the arm in the lymph node area. It subsided after a couple of days. This was more than likely linked to the bodies absorption of the depot thus decreasing the pressure against the nerve in the quad. Hope that helps. I agree with the others in that gyno should not have set in that quick since it would take a few days for hormone levels to increase in the blood.