Weird spot?

So I’ve had this weird purple area on my butt that looks like a bruise but it feels grainy and hollow it’s a little freaky. I mentioned it to my OBGYN the other day and she said it almost seemed like fatty necrosis and to pay attention to what I’m doing and asked me if I leaned on anything that could’ve caused that. I didn’t get an answer from her so I did some research on fatty necrosis and it doesn’t look like it at all. Fatty necrosis is a lump and mine isn’t it’s flat but when you feel it it’s like hollow grainy space 🙄 idk what it is and it just freaking me out 🤦🏻‍♀️ you can’t really see it but it’s just making me uncomfortable cause I don’t know what it is i