I just noticed there is a tiny dinge on my new MacBook Air's lid. The machine itself is perfect and functions well, but just wondering if I should inform Apple as it would have come with this.
I don't know what Apple's new purchase customer satisfaction policy is in Northern Ireland, but it's really up to you to decide whether or not you want to live with it as it is not functional damage.
Since you didn't bother to attach a photo, there's no way for any of us here to assess the ding.
Personally, I'd probably try to get them to replace it. I tend to keep my Macs for many years, so I'd might as well start with something pristine. But that's just me...