Pain in feet. Disease. please advice.

I'm a regular walker and for the first time I got this pain in the lower right side of the right feet while I was walking. The pain gradually increased the next day and worsened. It's been 4 days now, the pain has reduced but I notice slight pain on the heel bone, ankle and surrounding areas and is no longer in the lower muscle area of the feet where it originated. It is manageable and I can walk well with mild pain now. I wanted to know if this is normal because I've never experienced this and I've always been fit and active. A physiotherapist suggested this could be a muscle pull or calcium deficiency and also gave me feet reflexology therapy. I don't think this targetted the affected areas but it's reducing every day. I'm concerned if this could be related to any underlying disease. Please advice.