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

https://andresqthf131.yousher.com/back-pain-chiropractor-after-accident-sciatica-linked-to-whiplash-what-to-do

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