little brown flake

My period was due yesterday but today this morning it still hasn't come yet. But when I woke up I saw on my panty liner a small brown flake and I was wondering what that could mean.
I've had my periods before and I usually start them with quite a lot of brown blood.
I'm a little nervous and I hope it comes
I didn't have anyone ejaculate in me. But two days before my period my bf and I just tried to put the tip in and we took it out after 5 seconds bc it hurt. Prior to this happening I already gave oral sex, he came, peed and washed w soap and water. Pls any help would be appreciated