Help...!!!

[JessicaMay]

Hi I'm currently on day 23 of hatching my duck eggs! Whilst candling them last night there was no movement in one of the eggs and there was a dark almost black blob near to the air cell. See photo below

I have put the egg back in the incubator for now hoping for the best, but does it look likely that I have lost him??

Thank you so much,
Jess