How to stop nail biting and fix damaged cuticles?

Hmm, I’m not much of a nail biter myself, but I definitely remember those days when little bits of dry skin or hangnails would drive me crazy enough to start picking at them. I know exactly what you mean about how every single little mark becomes glaringly obvious once you soak your hands in water,

The smartest move is really just to stop picking altogether. To make that easier, you might need to clear away that excess skin first and then commit to using a good moisturizer so the urge to pick doesn't come back,

I personally find it helpful to use an exfoliant, or even just gently smooth out the edges with a pumice stone after a shower—just be careful not to go too hard and hurt yourself,
As far as a routine goes, applying a bit of cuticle oil and following it up with a heavy, nourishing cream before bed works wonders,
and during the day, whenever you remember—ideally right after washing your hands (maybe keep a tube in the bathroom?)—apply a hydrating hand cream that absorbs quickly,
It takes a little extra effort at first, but once you’ve repaired the underlying damage, you should find that a simple once-a-day application is more than enough to keep things under control.

I wasn't even talking about my cuticles, I mean I'm more of a skin-picker around the tips of my fingers and stuff

Honestly, I do the exact same thing and it is just plain gross... Apparently, there’s actually a clinical connection to OCD, and they call it dermatophagia. If you're looking for a way out, maybe try grabbing some of those bitter nail polishes? You know, the ones that taste absolutely revolting if you get near them... that might actually help you kick the habit.

I guess I used to have this weird thing where whenever I’d bite my nails, everything I ate afterward would taste all bitter and gross, so I'd just lose my appetite entirely, maybe because it was so revolting...

I’ve never actually given them a shot myself. I really do try to keep it under control, but it always seems to happen subconsciously... you know how it is? My fingers are looking a little better now, though I've got this one specific spot that's just completely shredded and I can't seem to stop picking at it. Honestly, the best trick is probably just wearing gloves all the time so I can't even get to them (:

If you’re looking to get skin healing moving faster, St. John's Wort oil is my absolute go-to... $11 You can pick it up at any local drugstore, and honestly, I’ve wasted my time—and money—on countless creams 🙂 —I mean, seriously, I've tried a ridiculous amount of them
—but none of them have lived up to it.

So yeah, give it a shot if you want something that actually works.