Dark pixels (not dead)

[mfg_lv]

So this appeared today:

I have no idea what it is. It doesn't look like a dead pixel to me, and yet it somehow almost acts like one. It's basically black if you look at it from a distance.
The monitor is Dell P2414H, IPS LED, I've had it for 6 months or so.
I tried some software for stuck pixels for like 3 hours and I tried the push method but it didn't actually do anything. I also cleaned it if someone asks, it's not a stain on the monitor.
Any ideas what it is and if it is possible to do anything ?

 

[Deders]

Is there a LCD Conditioning option in the monitor's menu? on my dell it's in the other options section.

 

[mfg_lv]

It has, it doesn't do anything to the pixel.

 

[AdamK47]

It's most likely dust that's stuck on the inside.

 

[mfg_lv]

It's most likely dust that's stuck on the inside.

On which layer ?
It looks like it may be between the LED and the pixel, casting a shadow.
How do I remove it ?