I have really scratched my head with fire by asking the question!

One option that avoids the serious danger/harm implied by such expressions as "walked into the lion's den," "put [one's] head into a noose," and "cut off [one's] nose to spite [one's] face" is the more pedestrian—literally and figuratively—expression "put [one's] foot in it." Here is the entry for this expression in Christine Ammer, The American Heritage Dictionary of Idioms, second edition):

put one's foot in it Make a blunder, as in I didn't know it was a surprise party; I guess I put my foot in it. This expression presumably alludes to setting one' foot down in mud or excrement. {Late 1700s}

The blunder in Ammer's example is unexplained, but it probably involved the speaker's ruining the surprise of the surprise party by giving it away to the guest of honor. The trouble that the speaker incurs as a result of this misstep is simply that the planners of the surprise party may be annoyed at the speaker for the untimely revelation.

The expression "put [one's] foot in it" is used for just such instances of faux pas as this one. No one suffers serious injury or other damage, but the person who has acted incautiously, indiscreetly, or insensitively is left with the social equivalent of a very messy shoe as a result. The related phrase, "put [one's] foot in [one's] mouth" is more narrowly concerned with errors in speech (or by extension, writing), so it would work in Ammer's example above but not in a case where the blunder was nonverbal. For example: The pie was delicious, but I didn't realize that my spouse had been planning to bring it to a book club meeting tonight. I really put my foot in it this time.

"I cannot think of a direct equivalent, but "Putting your head in the noose", is possibly close.

This refers metaphorically to someone voluntarily placing their head in the hangman's noose, and allowing themselves to be killed (hung). That is, bad things happening as a result of their own actions.

Possibly: ADD INSULT TO INJURY