I've been concerned about developing ingrown toenails (onychocryptosis). I suspect it is related to footwear. According to one old study conducted in China and India, barefoot people never suffer from onychocryptosis.
http://refs.ahcuah.com/papers/shulman.htm"No instances among the barefoot feet were found of: Onychocryptosis, Hyperidrosis, Bromidrosis, Hallux Valgus, Hallux Varus, Bursitis at the first or fifth metatarso phalangeal articulations.
Without footgear that interferes with nail growth, and because these people allowed their toenails to grow long and did not have the habit of digging into the corners of their nails when cutting them, onychocryptosis did not form even when nails were malformed. The resulting complete absence of onychocryptosis should serve to prove that proper nail care plus nonrestrictive footgear are all that is necessary to prevent the condition even in the presence of congenital nail malformations that are considered predisposing factors."
I'm not a doctor, but perhaps you could try a few things, like switching to hiking sandals with very little or no arch support. You might be surprised at how comfortable they are.