This sounds more like my problem...

Plantar fasciitis. Stress on the bottom of the foot sometimes causes arch pain. The plantar fascia, a supportive, fibrous band of tissue running the length of the foot, becomes inflamed and painful. If arch pain persists, consider investing in better shoes, an over-the-counter support, or see a doctor of podiatric medicine for a custom-made orthotic device to insert into the shoe.

Although the worst pain is generally at the back of my heel, rather than my arch. Hmmm...still googling.