To feel pain or discomfort
When to use
Feeling body pain, Cold symptoms, Having a headache
The nuance
Use 아프다 when expressing pain, discomfort, or soreness in body or mind. It applies even without visible injury.
아프다 (a-peu-da, apeuda) · 다치다 (da-chi-da, dachida)
아프다 mainly expresses pain or discomfort, while 다치다 refers to having a physical injury or wound.

One lane per word — no nested boxes, just the gist.
To feel pain or discomfort
When to use
Feeling body pain, Cold symptoms, Having a headache
The nuance
Use 아프다 when expressing pain, discomfort, or soreness in body or mind. It applies even without visible injury.
To get a physical injury or wound
When to use
Getting a wound from falling, Injured in traffic accident, Cut by a knife
The nuance
Use 다치다 when someone gets a visible injury or wound from falling, hitting, or accident.
머리가 아파서 약을 먹었어요.
meo-ri-ga a-pa-seo yak-eul meok-eoss-eo-yo., meo ri ga a pa seo yak eul meok eoss eo yo.
아프다 is correct for expressing headache pain.
머리를 다쳐서 피가 났어요.
meo-ri-reul da-chyeo-seo pi-ga nass-eo-yo., meo ri reul da chyeo seo pi ga nass eo yo.
다치다 fits because there is a visible injury on the head.
손가락이 아파서 붕대를 감았어요.
son-ga-rak-i a-pa-seo bung-dae-reul gam-ass-eo-yo., son ga rak i a pa seo bung dae reul gam ass eo yo.
아프다 is correct for finger pain.
손가락을 다쳐서 붕대를 감았어요.
son-ga-rak-eul da-chyeo-seo bung-dae-reul gam-ass-eo-yo., son ga rak eul da chyeo seo bung dae reul gam ass eo yo.
다치다 fits because there is injury on the finger.
감기에 걸려서 다쳤어요.
gam-gi-e geol-ryeo-seo da-chyeoss-eo-yo., gam gi e geol ryeo seo da chyeoss eo yo.
You cannot use 다치다 for illness without injury; 아프다 is correct.
넘어져서 아팠어요.
neom-eo-jyeo-seo a-pass-eo-yo., neom eo jyeo seo a pass eo yo.
아프다 can be used to express pain after falling.
넘어져서 다쳤어요.
neom-eo-jyeo-seo da-chyeoss-eo-yo., neom eo jyeo seo da chyeoss eo yo.
다치다 is correct if falling caused injury.
기분이 다쳐서 슬퍼요.
gi-bun-i da-chyeo-seo seul-peo-yo., gi bun i da chyeo seo seul peo yo.
다치다 is for physical injury, not emotional hurt.
Which is correct when your head hurts?
You fell and got a wound on your knee. Which word to use?
I caught a cold and my body is ___.
What does it mean?