Mine has this as well I keep trying to clean it but it doesn’t come off. I assume it’s a scar from the cord 🤷♀️ 16 weeks and it’s still there.
We had this and the GP told us it was an umbilical granuloma (google it and the NHS has a helpful leaflet). It doesn’t hurt them and we treated ours with salt (I’d get it checked with the GP first though!).
My little one had the same thing (umbilical granuloma and mentioned above). Mentioned it to my GP and they put a bit of silver nitrate on it that made it disappear after 2 weeks or so. Stings as it's being put on but is fine after a couple hours
My little ones is the same. Pretty sure it’s from the cord!