Lastimar vs. herir vs. hacer daño

The Spanish language, like English, has multiple words to express the concept of causing pain or hurting - three of which are 'lastimar', 'herir', and 'hacer daño'. While they can often be used interchangeably in some contexts, these words have some distinctions.

Lastimar

'Lastimar' is generally used to refer to physical injury, particularly minor ones though it can also apply to emotional harm.
Cuando jugaba fútbol, me lastimé el brazo.
(When I was playing soccer, I hurt my arm.)
Sus palabras me lastimaron.
(His words hurt me.)

Herir

'Herir', similar to 'lastimar', largely refers to physical injuries, although it tends to hint at more serious wounds. It's also used metaphorically for emotional or psychological injuries.
El soldado fue herido en la batalla.
(The soldier was wounded in the battle.)
Sus mentiras me han herido profundamente.
(His lies have deeply wounded me.)

Hacer daño

'Hacer daño' is more versatile in its usage as it's used to express both physical and emotional pain. This phrase could also mean damaging objects and not just persons.
El alcohol puede hacer daño al hígado.
(Alcohol can damage the liver.)
No quiero hacerle daño pero tengo que decirle la verdad.
(I don't want to hurt him but I have to tell him the truth.)
El terremoto ha hecho mucho daño a la ciudad.
(The earthquake has done a lot of damage to the city.)

Summary

`Lastimar`, `herir` and `hacer daño` all suggest inflicting pain or injury whether physically or emotionally. Their use comes down mainly to severity and context. However, these differences are nuanced, and regional usage can vary.