It's not a big deal / 大丈夫だよ/大したことないよ

It’s not a big dealは、「大丈夫だよ/大したことないよ」という意味です。


A: Oh no! I booked the wrong time for my bus. We have to leave tomorrow morning for the airport. What shall we do…?
B: Relax. It’s not a big deal. We can still call to change the reservation. If it’s full, you can use the express train.
A: Oh, ok… Shall we call them now?
B: Sure, I have their number.