Oh god I wish you could have seen my face when I saw your "tiny mistake". But to tell you the truth it gave the final piece an awesome look.
I work traditionally just as you, this happened very recently, I was working on a guest art and I drew 3 illustrations, when I was going to ink the one I liked the most I ran out of ink, so I opened a bottle that a friend of mine gave me as a present, when I tested the ink, it was too thin, wow, it was almost water, and I was thinking that the deadline was coming closer, so I let the bottle of ink open to let it dry a bit.
I waited almost a day, the thing got better but not to the consistency I like, it was thin and it took a little more time than I'm used to to dry (it's time to mention that the paper I used was thin too, so that thing could break in any minute).
So I said, f*ck it, I'm gonna ink with this I can't lose anymore time, I went inking with it and everything was fine, until I remembered that this thing took longer to dry. When I took my hand off the paper and saw a big ink splatter on the character's shoulder..................................... my heart stopped for a minute.... I was like oh sh*t I ruined this............
Gladly I covered it up making some lines thicker, but since we don't have an undo button, inking is like walking on a tightrope @_@