Before ink critique, a word about nostrils: I am not an expert but I think they need some further work on where they connect with the face, especially the left (ours) one.
Sorry I killed that extra bit of hair, I kinda floodfilled it out by mistake!
Okay, first of all, your drawing is pretty awesome. It has character and it's very well made fundamentally. That being said, this is not ink, this is tightened pencil work, if you get my meaning. If there's no point to the ink then don't ink it. The ink needs to have some identity of its own. How I did it is one out of hundreds of ways to ink, but you can tell it's ink now. It's sharp (no grays) and it has its own little ruleset (the cross-hatching theme) that the eye interprets. That's the biggest thing I have to tell you really: make the ink do something, not just follow the pencils conservatively. Especially on the lips the inks really don't define the shapes as well as they could in your original. And do try to give a hint of teeth there (though i understand you'd rather avoid EVERY TEETH OUTLINE
for obvious reasons) because whitespace is kinda odd for that.
Furthermore I did some airbrush and tone work but that's just extra. I mainly did that because the short of shadowing I wanted on the face couldn't easily be done with ink lines (too many lines and a woman's face becomes a grandmothers face) but also to remind: inks do not have to stand alone. Comic tone and airbrush work and whatever else you desire that lives an sharp 1bit print are the friends of ink.
Tell me if you'd like me to clear something in particular out. And here's a photoshop file for you of the same thing layered
if you need it
edit: it was pointed out to me that I perhaps wasn't clear enough: the biggest issue with how you ink is blurryness/softness. Turn off AA in photoshop and work at large sizes (600 dpi or something, the PS engine will aa somewhat when you zoom out, which is fine and nondestructive and the pixels won't bite you) or just get Manga Studio if you want to keep inking digitally.