It was surprisingly much less painful than I was expecting. The first 10 minutes were a bit ouchy, then the adrenaline kicked in. The shading hurt a bit more, but there isn't a lot of it. I'm under 5 hours out and it doesn't hurt at all, it isn't oozing and I can moisturise it without pain. Mind you, it's delicate linework - if I were having serious blackwork or colour, it would hurt a lot more. Ditto if I picked another part of my body - upper arm is easy.
I'm so happy with how it turned out, the artist who did it is a specialist in this sort of delicate stuff.