Arcane Vigor

Source: Player's Handbook

Level 2 Abjuration (Artificer, Sorcerer, Wizard)

Casting Time: Bonus Action
Range: Self
Component: V, S
Duration: Instantaneous

You tap into your life force to heal yourself. Roll one or two of your unexpended Hit Point Dice, and regain a number of Hit Points equal to the roll’s total plus your spellcasting ability modifier. Those dice are then expended.

Using a Higher-Level Spell Slot. The number of unexpended Hit Dice you can roll increases by one for each spell slot level above 2.