Egg on day 15 and I noticed a problem please help

[chicken pickin]

I have a Marans egg that is on day 15, I was candling tonight and I noticed a problem. 1st the aircell is on the bottom pointy end side and 2nd there are small cracks on the same pointy end. The egg is dark and looks like A) it is developing a chick or B) its filled with bacteria and is a nasty egg bomb waiting to happen ther is no smell though. I need advice on what I should do. Has anyone ever encountered this that can help? Thanks so much.

 

[fogandcopper]

here the air cell is is fine. I have had them dead center on the side. Chicks miss it 75% of the time anyway. The cracks should be okay just try to leave it alone as much as possible.