"I didn't mean to" is often used to express regret or apology for something that the person did or said unintentionally. It is a way of acknowledging that the action or words in question may have caused harm or offense, but that the person did not intend for this to happen.

For example,
i) "I didn't mean to hurt your feelings" suggests that the speaker may have said something that was inadvertently hurtful, but did not intend to cause harm.