Too many things hurt!
Triathlete Steve Smith after winning his age group and a slot in Ironman Hawaii, and turning it down!
Foot pain in the triathlete is ubiquitous and one of the more common diagnoses is a stress fracture. Classically, they're know as "march fractures" and described in the second metatarsal, but they've been noted in all the metatarsals, as well as several other bones in the foot. In runners, the most common location is in the neck of the metatarsal where ballet dancers, for another example, see them in the base of the metatarsal. They occur
due to excessive, repetitive stress applied to a bone that lacks the structural strength to withstand it.
Predisposing factors include increase in physical activity like boot camp or deciding you want to do a triathlon, previous immobilization, diabetes, etc. They're frequently found with the Female Athlete Triad of disordered eating, amenorrhea (menstrual irregularities), and osteoporosis.
If your xrays reveal a stress fracture, occasionally all that's needed is protective footwear such as hard soled shoes although some people are casted until they're pain free. Recurrence of the pain indicates the need for further rest. Once pain free, normal activities and footwear are resumed at a restricted pace allowing for a more gradual increase in stress.