The Healing Stone

Upon death, the player would lose half a heart from their max health permanently. The only way to fix this would be to find the healing stone deep underground.

The healing stone would come as a red ore similar in color to the healing potion, and would have an animation of the enchanted glow. It would give off a light level of 1. When mined, it will only ever drop 1, and will only drop anything if mined with a diamond pickaxe or greater. It will generate in veins of 1 only and would be about as rare as netherite.

To use it, you would hold it and press the left trigger (right-click for you, java users). It would then be used up and restore a half-heart to your max health until your max health is fully fixed. Alternatively, it could also be used in the smithing table to add an enchantment to your armor that gives you regeneration 1 when worn.