In reply to:
Well believe it or not, not all erections are sexual. You can get erections from simply being nervous, which I suspect may have been what happened to you.
I agree. Some guys get erections when nervous, which was probably your case. Although you're bi, it doesn't sound from your post that you were sexually turned on by anything. It doesn't sound like you were staring at every one else's penis and getting turned on by the site of them, or thinking what you would like to do with them, etc. So I don't think that matters that you're bi.