1 doctor weighed in: Why is my hand swelling after injury? 1 doctor weighed in Want a second opinion? Simply is a sign of injury and or inflammation, or infection blood or fluid accumulated in tissues due to broken blood vessels or fluid shifts from histamine release near inflammtion or due to tissue destruction from infection. In brief: Swelling quite. Simply is a sign of injury and or inflammation, or infection blood or fluid accumulated in tissues due to broken blood vessels or fluid shifts from histamine release near inflammtion or due to tissue destruction from infection. Would you like to video or text chat with me?