boo-boo

1. A stupid mistake; a blunder: "the petty talking points, peripheral issues, tactical boo-boos, and small-bore scandals that regularly intrude on campaigns" (New Republic).
2. A slight physical injury, such as a scratch.

[Perhaps alteration of boohoo, to weep noisily.]

The noun has one meaning:

Meaning #1: an embarrassing mistake
  Synonyms: blunder, blooper, bloomer, bungle, foul-up, fuckup, flub, botch, boner