Needed To Vent Urgently😭

I'm 15 and I just lost my virginity last night to my boyfriend in his room. It was going well and I was really feeling him and myself. Someone started to knock on the door. It was his sister. I had to hide behind the bed. When she found me in there, I had been able to get dressed quietly and quickly. I flat out lied to her that we hadn't done anything. I feel bad for lying and now I feel really nervous around her... She's my best friend. Please, no judgment.