Yep, I was thinking of a Morton's neuroma as well - swollen bundle of nerves. It's more common to get them in the metatarsal area between toes 3 & 4, but you can get them anywhere in your foot. Painful buggers. I've heard some folks have had good luck with cortisone shots if they don't want to resort to surgical excision.

I have had some very mild neuromas in my feet for years, as long as I wear wide enough footwear they don't get aggravated and I can manage the situation just fine.