That happened to me once. Freaked out. Rang ABA. They told me it could be inflammatory breast cancer (among other things - they weren't trying to be unhelpful, just something they were obliged to mention). Freaked out even more.

Went to GP. GP said everything was fine. Sent me for a breast ultrasound just to make sure. It was all fine and never happened again.

Baby was fine. Blood does irritate their tummy a bit but in a couple of years when they are pretending to be superman you realise swallowing a bit of blood is totally fine.

And we all lived happily ever after. I'm sure you will too, but go see your GP if you're worried.

Not trying to be flippant - just wanting to reassure you