My little brother snuck into my room while I was masturbating to some pics on my computer.What should I say!?

I was looking at some pics of different movie actors online and my back was turned to the door. My 7 year old brother snuck in when I was using my vibrator and walked up next to me and said, "Eww, what are you doing?" I screamed and jumped up with the wet vibrator still buzzing in my hand and screamed for him to leave. I haven't talked to him since and I don't know what to tell him. How do I explain so that he doesn't become a pervert or something?