While doing a drop set of tricep pushdowns, I felt an ab poping out of place, with a good pain following, it only lasted a few long seconds.
A few minute later while bending I felt the same pain, again very temporary. I could really touch the ab, and it was that same ab that was pushing on my belly.
I remember having felt the exact same thing 2 and a half years ago, while I was a total newbie to weightlifting and only lifting once a week. It happened while doing the "touch the toes with straight legs" stretch. I think it was the same ab. So a inguial hernia is out of the question, anyway I think it is located in the lower abdomen.
By the way it's the ab on the left row (same left as heart), second from the top.
Worked the abs today, many hours before doing these pushdowns. Also, I stretched my hamstrings.