How do I say "it's okay" in Japanese?
I mean, a "it's okay, don't worry" kind of thing, where the other person has done something wrong and I need to tell them that it's okay. :)

Question

Answer

I would like to answer your question.

"It's okay, don't worry" means “大丈夫です。心配ありません。(Daijoubu desu. Shinpai arimasen)”. 
Or “大丈夫，心配ないよ(Daijoubu, Sinpai naiyo) ” is more a casual sentence.

I hope I can help with your Japanese studies.