Eating a little bit of moldy bread is not gonna do you any harm and is usually nothing to worry about if you do ingest a bit of moldy bread.
Still you might experience some problem after eating moldy bread such as nausea, abdominal pain, vomiting, or diarrhea, or fever, or cough.
If you do experience any of those symptoms after eating moldy bread then it would be a good idea to see a doctor about it but most times you'll be okay.
I've accidentally eaten a bit of moldy bread myself before and nothing happened although it grossed me out once I realized I ingested some mold and it didn't taste very good at all.