Black ring around nub

[Babychai]

Hey guys, i have female squirrel about 9-10weeks old now. Recently she developed a dark ring around her little nub. I’m not sure if i should be concerned or if it’s just part of the maturing process. Can anyone provide some insight? I will show a before and after photo.
Before
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After
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[redwuff]

Looks like coloration of the fur. I don’t see any problem. Beautiful baby!

[Babychai]

It’s not colouration of the fur though, i can tell that it’s the skin i will try to capture a clearer picture. It resembles a blister texture but i’m not quite sure. the dark area has the wrinkly type of texture. 309429

[Babychai]

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