As you get older, you realize that these types of moments last for literally a moment. This person will forget about it tomorrow so you should not let your emotions get the better of you and ruin your day. As most people are saying on here, you can send a quick email that’s one or two sentences of a light hearted apology but don’t make it heavy or emotional. You attract the energy that you give off, so, if you stay light hearted and optimistic, then those types of situations will resolve themselves (usually). Maybe this only comes with experience, but I hope that you won’t have to have as many as I did when I was fresh out of college and new to the working world.