The speaker imagines carrying a worn-out heart to someone else, a "you" who is never named. The speaker is old and in pain, and the heart is not offered as a gift to be proud of. It is "ugly as the mother of a wound," a striking phrase that suggests something even rawer than an injury, the source that keeps producing hurt. Coming to this person means showing the worst, without dressing it up.
The last image changes the mood. A sea "alone with a captain / in the middle of a sound sleep" is oddly peaceful, though also a little unsettling. The captain is asleep, so nobody is steering, and the sea is simply there, vast and unwatched. Perhaps that is what the speaker hopes to find in the other person: a place where defences drop and the pain can rest. The poem feels tired, tender and vulnerable, and it stays quiet about whether the speaker will actually arrive.