Hematomas can form under the skin after impact, leading to swelling, discoloration, and pressure

https://telegra.ph/What-a-Doctor-Who-Specializes-in-Car-Accident-Injuries-Does-for-Whiplash-07-09

Hematomas can form under the skin after impact, leading to swelling, discoloration, and pressure, sometimes needing drainage if large and painful.