Bloody Sharpening

With his bonus action, a caster passes a hand over a blade, magically sharpening it. For one minute, that weapon deals 1d4 slashing damage extra each time it strikes. In addition every time. In addition, whenever a creature with blood is hit by this weapon it suffers a Wound. At the end of the creature's turn, it takes 1 damage for each Wound it suffered.
A creature, when it heals itself in any way, loses a Wound for each hit point it heals. A creature can also heal a number of wounds equal to its proficiency bonus by making a medicine check with a DC equal to the caster's spell DC as an action. Each Wound heals after 1 minute of being inflicted.