大 丈 夫 私 が 行 く Note the long o, which results from jo + u — Tae Kim's Japanese Grammar flashcard

It's ME who goes (and not someone else).
Together with daijoubu, this is very interesting, the speaker expresses the following: "It's ok, calm down (daijoubu). [because] I go [and e.g. take care of the issue]". Note that what I put in square brackets is not explicitly expressend in dedicated words. It's the figurative meaning created by daijoubu + ga.