foot ‘click’ when walking

I am a 50-year-old male, 1.75m 65kg, very active runner/swimmer.
I have recently developed a distinct, slight ‘click’ in my left foot when walking barefooted on a hard surface. It is not painful in any way. On self-examination, I figure it’s occurring in the joint between the 3rd metatarsal and it’s phlanges. Wearing shoes it does not occur at all.
I am concerned that it may become substantially worse or is it perhaps a common, liveable event?
Thank you.