Sounds like a popping from the public symphysis area where the adductors etc attach aroudn the groin. Squeezing a cushion between the inner thighs can often get this pop and release. It is probably a generalised imbalance in your musculature and some might say some instability in your pelvis. Sometimes also it can be a boney instability in the very low back which can also feel that the pop is coming from the gropin. It's very likely nothing to worry about. Go see someone for an assessment and program of stretching and strengthening. On one off assessment and maybe a followup after 6 weeks of doing the program should suffice.