Well I'm not a doctor, but i knew it wasnt exactly safe. I also knew that its better to use sterile needles specifically made for this kind of play, and we did not which wasnt really a good idea. she made sure they were soaked in alcohol first and the area was also.
It hurt for maybe 3 days afterwards, not too terribly. This was sept of 05, and over the years she's probably done it about 5 or 6 times since then.
As to 'permanent damage' thats hard to quantify. I mean slip with a knife on your finger and you get 'permanent damage' in a scar. I am sure it left scar tissue in there, but we did get pregnant a few months ago so they seem to perform fine.