The word 困る (こまる komaru), or in the past tense or as an adjective 困った (こまった komatta) is used in a lot of contexts. Normally it's translated as 'be in trouble', but it means more than that. I actually can't think of one single English word that is its equivalent.
So let's see how it's used. It quite depends on the context, and the tone in which you use it.
First, to indicate you are in trouble, when you might say "uh oh", "oh dear" etc. in English:
定期をなくしてしまった。困ったなあ。 (Teiki o nakushite shimatta. Komatta naa.)
- I lost my (train or bus) pass. Oh dear (I'm in trouble).
寝坊した！ 困ったよ。 (Nebou shita! Komatta yo.)
- I overslept! Uh oh. (I'm in trouble).
Here's how to use it to indicate you are bothered by, in a dilemma, or embarassed by something.
マイケルにデートに誘われたのだけど、私はひろしが好きなのよ。困ったわ。 (Maikeru ni de-to ni sasowareta no dakedo, watashi wa Hiroshi ga suki nano yo. Komatta wa.)
- Michael asked me out on a date, but I like Hiroshi. I'm embarassed (in a dilemma / don't know what to do).
うちの犬はどこででもおしっこしちゃうのよね。 困った。(uchi no inu ha doko de demo oshikko shichau no yo ne. Komatta.)
- Our dog pees anywhere. Oh dear (embarassing, dilemma, annoying).
And here's how to use it to express anger/annoyance:
僕の自転車を勝手に借りないで！ 困るよ！ (Boku no jitensha o katte ni karinai de! Komaru yo!)
- Don't borrow my bicycle without asking! You're bugging me! (inconveniencing me, bothering me)
Finally, here's how to use it as an adjective.
あの赤ちゃん、困った顔して可愛い！(Ano akachan, komatta kao shite kawaii!)
- That baby has such a cute frowny-face!
Here is a classic children's song called 犬のおまわりさん (いぬのおまわりさん inu no omawarisan) - The Dog Policeman (おまわりさん is a familiar, sort of kiddy-way of calling a policeman.) See if you can pick up the phrase 困ってしまって (こまってしまって komatte shimatte), which means to be in a dilemma, in a pickle, not sure what to do, etc.
The dog policeman has to deal with a little lost kitten, who keeps on answering 解らない (わからない wakaranai) when asked, What is your name? Where do you live? In the end the kitten starts crying, so the dog policeman is 困った！
Here are the lyrics for the first verse, FYI.
迷子の迷子の子猫ちゃん (まいごのまいごのこねこちゃん maigo no maigo no konekochan)
あなたのお家はどこですか (あなたのおうちはどこですか anata no ouchi wa dokedesuka)
お家を聞いても 解らない (おうちをきいてもわからない ouchi o kiitemo wakaranai)
名前を聞いても 解らない (なまえをきいてもわからない namae o kiitemo wakaranai)
にゃんにゃんにゃにゃん にゃんにゃんにゃにゃん (nyan nyan nyanyan nyan nyan nyanyan)
泣いてばかりいる子猫ちゃん （ないてばかりいるこねこちゃん naite bakari iru konekochan)
犬のお巡りさん 困ってしまって (いぬのおまわりさん こまってしまって inu no omawarisan komatte shimatte)
ワンワンワワン ワンワンワワン (wan wan wawan wan wan wawan)
(Translation:
Little lost kitty
Where is your home?
Ask her where she lives but she says "I don't know"
Ask her name but she says "I don't know"
Meow meow meow
Little kitty just keeps crying
The dog policeman doesn't know what to do
Woof woof woof!
