Today’s mystery, what have I done to my wrist?

[bangandthedirtisgon]

I’m not worried or anything so not seeking medical advice as such but just wondering wtf could have caused this massive bruise on the inside of my wrist?

I was cleaning at the weekend and felt like it hurt as I’d banged it. There was what looked like a small puncture mark, it swelled up a bit and now a couple of days later looks like this.

Any ideas?

You banged it on something sharp which punctured a vein and it bled out under the skin. I've had bruises like that from cannulas. And once from giving blood.