After an ingrown toenail grew and went away by itself, my toe ended up red, swollen, and black. it has stayed like this for a while on two toes, why?

Infection: Black tissue is usually dead tissue. Red and swollen indicates possible infection. You should see a podiatrist.

Have it looked at.: Possible signs associated with an ingrown nail include: pain, increased redness, swelling, skin discoloration, bleeding, and drainage at the nail margin. The ingrown part of the nail is not always visible. Leaving an ingrown nail untreated could lead to the development of an abscess and possible underlying bone infection. Get it taken care of by a professional to avoid preventable complications.

Ingrown nail: Ingrown nails don't go away by themselves . See your podiatrist for assistnace - this is at the very least an infection.