Black foreign object in baby’s poop

Hi all, anyone has any experience with a foreign object in baby’s poop?? I tried googling about it but can’t seem to find a satisfactory reasoning behind it. My baby just turned 5 months and she has started to put things into her mouth. I used a cotton bud to pull it out of her stool and it was black and hard. I’m not sure what it is. Anyone? She doesn’t seem to be in pain at all. Afraid she might have taken something and put it in her mouth without anyone being aware of it as she’s being watched closely most of the time. Usually she has a teether or towel in her hands. #1stimemom #firstbaby