My Brother in law saw me naked what should I do?

[paradisegirl]

i have known my brother-in-law Nathan since I was 3 or 4. my parents died when i was 9. to get custody of me, my older sister married her boyfriend nathan. so i have been living with him since i was 9. now i am 14. on Tuesday my sister was out of town and Nathan was supposed to come home at 8. after playing soccer i came and decided to take a bath but i forgot to take a towel there. since no was home i was walking naked with nothing on to my room when suddenly Nathan showed up. i froze there for a moment in front of him. then i ran towards my room. I was so embarrassed. its been weird since then whenever I see him. what makes matter worse is that we are very close. he is like my own brother even like a father to me. he treats me as if i am his own daughter. its been 3 days now and i barely spoke to him. my sister is asking whats wrong with me. i want everything to be like before with him and me. any suggestions with this problem?
p.s. no one has ever seen me naked even my sister