Oof, that big toe looks angry 😬 From the photo it seems like the nail on the side is digging into the skin, plus there's some redness and swelling around the edge.
Looks like an ingrown toenail starting, or maybe already there. The yellowish edge + slight dark spot could also mean some trauma or early fungal change, but I can't diagnose from a pic.
What you can try at home right now:
See a doctor/podiatrist if you notice:
A podiatrist can lift the nail properly or do a quick minor procedure if it's infected. Way better than suffering for weeks.
Has it been hurting when you walk, or did something specific cause it like tight shoes or trimming the nail too short?
The best recommendation, being direct: see a podiatrist as soon as possible 🙏