If it's acute you need to see a doc, at least to make sure there's no underlying problem or infection. For the long term, I would recommend a visit to a good manicurist who could show you how grooming practice can help avoid the problem coming back. I come from a long line of ingrown toenail sufferers, and I can tell you that good nail care techniques make a huge difference. BTW so can diet -- have you made any major changes on that front lately?
Good luck
-Glenn