What happens when your finger turns black after trapping it in a car door?

When your finger turns black after being trapped in a car door, it typically indicates bruising or tissue damage due to the lack of blood flow or trauma. This can lead to a condition called hematoma, where blood collects under the skin, causing discoloration. It's essential to seek medical attention to assess for fractures, severe damage, or the need for treatment to prevent complications. Immediate care can help alleviate pain and promote healing.