Duck egg grey bruise ring

[Penfoldducks]

one of my duck eggs on day 24 has a grey ring around the outside of the shell. It lines up with where the airspace is. I can also hear tapping coming from inside l? What should I do

 

[Kellyjenny]

Can you please send a picture.

 

[Penfoldducks]

Can you please send a picture.

 

[Kellyjenny]

Never seen this let me find somebody who knows more about this. @DucksAreBest