Sore, red, swollen. It may even been lumpy and bumpy.
The edge of the nail is just digging into the toe, and it hurts to wear shoes!
It is an in-grown toe nail, and an infection of the skin.
Whatever you do, DO NOT cut the nail back! It seems counter intuitive, but it will only perpetuate the problem. This is because the nail will just grow into the toe again, and we will be back to square-one.
To settle the problem:
1. Clear the infection: usually this means oral antibiotics, but sometimes if the infection is not severe, bathing in antiseptic may be enough. Only when the infection has settled, can you proceed to the second step - otherwise it would be too sore!
2. Raise the nail: roll up a tiny ball of cotton wool, and secure it under the nail in order to raise the nail as it grows (over weeks/months). See the photo below.
3. Once the nail grows out, cut it so there is still at least 2-3 mm of nail left, especially at the sides.
If in-grown toe nails keep occuring, sometimes your doctor may need to remove a part of it permanently to prevent it from happening again.