Think nothing of it
Think nothing of it.and Don't give it another thought.; Don't give it a (second) thought.
1. You're welcome.; It was nothing.; I was glad to do it. Mary: Thank you so much for driving me home. John: Think nothing of it. Sue: It was very kind of you to bring the kids back all the way out here. Alice: Think nothing of it. I was delighted to do it.
2. You did no harm at all. (A very polite way of reassuring someone that an action has not harmed or hurt the speaker.) Sue: Oh, sorry. I didn't mean to bump you! Bob: Think nothing of it. Jane: Ihope I didn't hurt your feelings when I said you were too loud. Bill: Don't give it a second thought. I was too loud.