What Causes An Abdominal Knot After A Groin Injury With Pain?

I hurt my groin playing soccer. I began icing it immediately, and then the next day I have pain in my lower left ab. I reiced my groin and iced my ab. It got progressively better the next two days. Today I felt okay to lift weights, and did. Throughout my workout, it never was a problem until I did one exercise, so I stopped. Now, about two hours after my workout, I have no pain at all in the ab, but I feel a sort of knot in the ab, and it feels like it moves around randomly. I don't have a bump. What's wrong?