What has likely happened here (injury)?

I was in the gym, got onto a rowing machine, strapped my feet in, and then noticed that someone had left the handlebar up. When I was trying to reach for the handlebar, then person rowing next to me gave me a sudden push forward from my left, and I felt about two crackles to the left of my hip area. It basically felt like joints crackling, so it didn't hurt. If it was tendons, muscles or nerves snapping, I would have felt an instant pain right? So in the left hip area, (perhaps further to the left than the sacroiliac joint) what could that crackle have been?