Stimpak

This life saving injectable was developed during the great war by Aktos Pharma. It is a one-time use item that injects special stem cells into your body that immediately go to work repairing any wounds, both internal and external. Minor wounds are healed immediately, but it also goes to work speeding up your body's natural recovery process. While a consumer version hit hospitals and pharmacies worldwide close to half a century before the bombs fell, a special military formula also exists that can restore bones, entire limbs, and even gray matter instantly.

As a Bonus Action, simply remove the protective cover from the hypodermic needle, inject it directly into the part of your body nearest your injury, and squeeze the plunger to deliver the stem cells and recover 2d4+4 HP.