Black nail and finger

[Burakki]

Hello!

A couple days ago I noticed that my Syrian boy aged 6 months got something black on his nail and around its base, it looked like old blood. Today I noticed a black spot on the finger above that nail. The black around the nail is still there. I’m worried that it’s spreading.

Otherwise he seems absolutely fine. Runs in his wheel and climbs the bars and does all the stuff he normally does.

I’m attaching a photo. Help, please!