Silver Nitrate Bleg

A few days ago I went into the doctor to get a skin tag cut off (it was blocking my peripheral vision and annoying me). And cut it off he did. But first, he told a nearby nurse to get a silver nitrate stick in case there was bleeding. And there was bleeding, so the stick was duly applied.

Anyway, as this was happening I was thinking "Hmmm. Silver nitrate. I think I remember that from high school chemistry with Mr. Lantz. Stains the skin really badly and absolutely nothing gets it off, right?" Yes indeed. Stains it jet black, and as you can see above, the central spot where my skin was snipped is still jet black three days after it was applied. So my question is: just how long does it take until this stuff wears off? Any chemistry mavens around who either know or remember?