Boo boo and boo typically don't have the same meaning. boo boo can refer to:
1) (noun) a mistake, usually a small one, but humorously a large mistake.
2) (noun) a
small injury such as a cut or a bruise, used for children but humorously used for adults as well.
3) (verb; noun) the act of defecation (going
poo), or the
poo itself.
4) (adjective) general unattractiveness, lack of quality or badness.
Because of it is a relatively simple and humorous sounding word, it may have many more colloquial meanings within families,
friends or groups.
1) Jeffrey dropped a plate and it
broke, he made a boo boo.
2) Timmy fell off his bike and got a boo boo, he ran home to mommy so she could
kiss it and make it better.
3) "Lets
stop at the next restroom we find. I gotta go boo boo"
or
"I made a stinky boo boo!"
4) "Have you seen Duane's new car?" "Haha yea, that shit is boo boo!"