I’m so scared TMI

I had my second baby a little over two weeks ago via repeat c-section. Last week I noticed a marble sized hard lump in my groin area. I hurts to touch ir squeeze it there’s no head on it like it would be a huge pimple. It is just a rock hard lump the size of a marble right close to where my underwear would be. I have an OBGYN appointment tomorrow and I’m going to bring it up and I am so scared of what it could be. Has anyone ever had something similar? What did it turn out to be?