Caught Masturbating By Older Brother, HELP!?

Ok, I'm kinda freaking out. I'm 13, and my older brother just walked in on me masturbating. I know he saw me. Even though he saw me and I quickly stopped, he just started talking to me, something about the Origin of Chinese Checkers, as if nothing even happened?! My family looks down upon doing that, and I'm not sure what to do? I know hes probably going to tell my mom, and she will ******* freak out about it! Please help! :(