What Causes Discomfort In The Right External Oblique Muscle?

Hello, I have a concern over my right external oblique muscle. I was at the gym earlier, doing a combination of planks and legs lifts. Walking to my next exercise I could feel my right oblique was jiggly, for lack of a better term, not muscular like my left side. I finished my gym session without hindrance or pain. After inspecting myself further in the locker room, I noticed I could see my right oblique was swollen, and I could feel my muscle underneath what felt like fluid. No pain, just a little tender if I push hard enough. Any thoughts or advice would be appreciated. I ve never had a hernia but I thought they are more ball shaped and painful.