If I did a bad job cutting my big toenail, is there anything I should do to prevent problems?

I would say leave it alone, but… maybe keep an eye on it. Toenails will generally grow back the way they should grow. It’s not going to take some insane detour and imbed itself into your skin. I wouldn’t worry too much about it, really

This is what I would do:make sure it can’t easily get caught and tear off by trimming down the nail or filing. If you can don’t wear tight fitting shoes for a couple weeks. It will probably grow in just fine.

I think this depends on whose toe….

If you have diabetes it could be serious.

Nails grow out from the cuticle line and not the sides. So if the remaining piece is torn all the way across its bottom portion and just still embedded in the side (why it’s still attached), it would be better if it were removed. If left there, it will most likely cause a problem as the lower portion of the nail continues to grow out.

Since it currently doesn’t hurt, my guess is that it would be fine to remove the remaining piece at home. If the tear goes pretty far down, there is a risk of tearing it away from the skin underneath, causing bleeding and sensitivity. And as always, when in doubt, call on a foot doctor (not a pedicurist). As @Ltryptophan points out, if you have diabetes or circulation problems, make an appt. with a doctor to look at it.

I don’t have diabetes or foot problems.

This has happened to me several times. I would say clip as much as you can on the piece sticking up. If you rip it off you have a 50/50 chance of it becoming ingrown or mildly infected. I’ve been to the podiatrist twice because of this. The problem is that my toe nails, especially the big toe nail grow very slow and I don’t often have much nail to play with when trimming them.