My daughter woke up with this huge spot on her foot I don’t know what it could be. She’s been in pain and can’t move her foot what is this.. Explain this

A blood blister can be startling at first sight—a dark red or purplish bubble beneath the skin that seems to appear out of nowhere. Although they’re generally harmless, blood blisters can be uncomfortable and may sometimes indicate an underlying issue. Knowing what blood blisters are and how to care for them can help you manage them properly and recognize when …