Instep Lump

There is a pea-sized protrusion in the center of the instep (bottom) of my left foot. It only hurts if my foot is flexed upward and I press on it. No pain at all otherwise. It's been present for over a week, without any apparent change. I don't remember injuring it, but I walk a lot. Should I make an appointment with my podiatrist this week? Next week if it's still there?
[Female, 54 years, reasonably good health.]

[FootDoc]

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The instep is on the top not the bottom of the foot, but if it IS on the bottom of the foot, it may be a Dupuytren's nodule, thought that is only a guess and is not to be relied upon. All lumps MUST be evaluated by a hands-on examination of a qualified doctor, and the sooner the better. THAT is my recommendation.