Dismantle-san and Griffith-san, Interesting! Dismantle-san is right. We use だいじょうぶです to say "No thank you" in a soft way. It could be too vague, so you may want to add いいえ before だいじょうぶです.
I used だいじょうぶ a lot in Japan when the guy at 711 asked me if I wanted my chicken skin microwaved or if a server tried to show me a menu on the street in Sakae. I learned it from native Japanese people using it in those instances.
Another good opportunity for Kanji!
"あぶない" is written "危ない," with "危" being close to "厄" ("やく; Misfortune.") [Good way to remember how to write it.]
"痛い" (いたい) is commonly seen in the phrase which disdains Otaku-fied vehicles, 痛車 ("いたしゃ; Painful Car.")...
大丈夫 (だいじょうぶ) is a good set of a characters is get acquainted with, because this is how you'll see it written, mostly.