Is it possible to get a muscle cramp right below the rib cage and would it feel like a rock?

I’ve been sitting here typing and all of a sudden I feel uncomfortable under the right side of my rib cage. I stood up and it feels really hard on that side. It doesn’t feel like a muscle cramp but rather like a large rock is sitting there. The other side is soft an not painful. It hurts to press it. I know many will say to go to the doctor but its too late right now and for all I know it may be gas. But this isn’t a sharp pain nor does it feel like bloating and if it is a muscle cramp, I certainly didn’t do anything to make it happen.
Is there a way to tell if its a muscle cramp?