Large black/purple insect bite?

[tj_06]

I noticed that a few days ago a deep red, regular shape on my arm just above my wrist appeared.  It has grown much bigger since  and is now a purple/black irregular shape approx 10mm by 20mm at the widest point in each direction.  What appears to be a hole in the center has appeared too.  It isn't tender or raised but looks quite nasty.

Has anyone any ideas please?

[mombojombo]

Go to the doctor! You didn't see any bug bite you there? Is it one hole or two in the center?  If it is two, it could be a spider bite. If it is singular, it could be a mosquito or tick.  If it is a tick and you get rings like a bulls-eye, see a doctor immediately.  Lyme disease is scary and you can get antibiotics to fight it especially early. If it is not disappearing, I'd head to a doctor pronto if it were me.

[tj_06]

Thank you mombojumbo, I think that I had decided that as it seems a bit bigger today and is still as dark.  I will let you know how it progresses.