"Warui ja nai" for tattoo

I am designing a tattoo and would like to use the Japanese kanji for the phrase "I am not bad" which I understand in Japanese shorthand to be "Warui ja nai" (please correct me if I am wrong)
I know the kanji for "warui" is わるい but I am having trouble with "ja nai". Could anyone help me with this?

わるい is hiragana (phonetic writing), not kanji at all, first of all.

Sorry but "warui ja nai" is not correct if you want to say "I'm not bad/wrong." The best you can get to is "Warukunai." There is a kanji for the part "waru-" but the rest needs to be in hiragana (phonetic writing.) There is no way to write it all in kanji - and personally I don't think it's cool to have a plain sentence like "warukunai" as a tattoo, though I admit it's up to you.

Oh, if you want to say "I'm not a bad/delinquet guy (though you might assume that/I might look like that)," then you could say "waru ja nai" (notice the subtle difference from "warui"), but that's still a very plain sentence.

The Chinese uses kanji for everything they write.

http://www.funnyjunk.com/funny_pictures/245310/Literally+Stupid+Tattoo...

don't get a tattoo in a language you can't speak!! goofy alert!!

That would be one goofy looking tattoo. I'd suggest you look for another language (like the aforementioned Chinese).

If a Japanese person saw something like that, they'd quietly laugh behind your back.

I'm also not a fan of that as a tattoo (I think it'd look better in English), but if that's what you want then the Japanese looks like this:

warukunai - 悪くない
warujanai - 悪じゃない

Be sure to update with a picture once you get the tattoo done.

Nowadays, regular posters post lame fonts without mentioning the risks ;)

Hahaha, I think you guys have thoroughly mentioned the risks, and anyway I'm just taking a page from dave ;)