Learn Russian: Ты нечаянно отдавил мне ногу и зацепил куртку! - You accidentally crushed my foot and snagged my jacket!

This is the Dative of inalienable possession (also related to the Ethical Dative of detriment). In Russian, when an action happens to someone's body parts or clothing—especially when it hurts or affects them negatively—you use the dative pronoun (мне) to show who is affected, rather than a possessive adjective (мою). Saying мою ногу would sound unnaturally detached, as if the foot is just a disconnected object you happen to own.

Does the мне also apply to the second part of the sentence with куртку (jacket)?

Yes, it does. The single мне acts as the dative of possession for both actions: the person crushed my foot (отдавил мне ногу) and snagged my jacket (зацепил [мне] куртку). Because clothing is worn directly on the body, it often takes this same "inalienable possession" grammar when something happens to it.

I usually use наступил на for "stepped on". How is отдавил different?

Отдавить implies a much heavier, more damaging impact than just наступить (to step on). It comes from the verb давить (to press, squeeze, or crush). Using отдавил мне ногу means the person stepped on it so hard that it felt crushed or caused significant pain, which fits the agitated tone of the sentence.

Why use нечаянно instead of случайно for "accidentally"?