HELP my sister caught me naked?

I was in the shower and i realized that i forgot to grab some new cloths (mine were dirty from playing football) and i ran out of my room really fast and grabbed some clothes, so i walked out of my room and she was on her way to the bathroom! I guess she heard i was done in there, She said "oh sorry" and quickly turned around and went back to her room and giggled a bit. Please tell me what I should tell her I am sooo embarrassed, And fyi she is 21 and i am 14.