Hi there -
You may have suffered an intradelivery herniation of one of the inguinal muscles, or perhaps just a pull or tear in that area. Since it took months for the
pain to develop it's probably not a hernia, but it still could be. It also could be a nerve beinng impinged upon, again probably due to pregnancy or the delivery. Muscles are weakened and stretched prior to and during delivery of a baby, and a weakened muscle can eventually herniate or become inflamed. I'd have this looked at before it has a chance to progress, on the off-chance it may actually be a hernia or muscle on the verge of herniating.
I hope this is helpful. Please follow up with us here, and if there's any more to the story, please fill in any blanks. Best of luck to you.