My DH suffered an ingrown toenail only a couple of months ago. He kept picking at it, and making it worse, until it was all swollen and feral. He went on antibiotics, which helped a little, but then the doc had to give him a couple of locals around his toe (very painful - sorry!) then she had to cut away some of the swollen flesh then cut out half the toenail, he ended up with stitches, and was on painkillers for days. He couldn't walk on his toe properly for days afterwards. Moral to the story? Don't leave it as long as my DH did. And whatever you do, don't cut at the bit of toenail growing into your skin, it will only make it worse. One of the best things to do is cut a 'V' in the middle of your toenail, which will encourage your toenail to grow in, rather than out IYKWIM??
Hope that helps!