Odaiji ni means "Take care of yourself" or "Get well soon." This phrase is used when someone is ill or recovering from an illness. It expresses concern and wishes for their quick recovery. You say this to someone who is feeling unwell. For example, "無理しないで、お大事に。" (Don't overdo it, take care of yourself.).

病気(びょうき)の人(ひと)や体調(たいちょう)が悪(わる)い人(ひと)にかける言葉(ことば)です。体(からだ)を大切(たいせつ)にしてほしいという気持(きも)ちを伝(つた)えます。「お大事(だいじ)に。」