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 develops when tiny blood vessels (capillaries) under the skin break while the outer layer of skin stays intact. The leaked blood becomes trapped beneath the surface, forming a raised, fluid-filled spot that looks red, maroon, or purple—noticeably darker than a typical clear blister.

Blood blisters most commonly appear on:

Fingers and palms

Toes and soles of the feet

Inside the mouth (cheeks, tongue, or gums)