Foot Pain/Swelling

The past few days I have been experiencing a pain/soreness on the top of my right foot. I first noticed the pain/soreness to touch last week.
Since then I have noticed the top of my foot from about the middle of my foot up to the toes has become swollen and puffy.
It is tender to the touch but I can walk ok and move my toes.
There is no bruising or cuts or anything and I can’t think of anything that I have done in the past week or so that would have caused it.
I do wear heels during the week as my job is corporate dress, but I have never had anything like this happen before and am a bit concerned.
I do go to the gym usually 2-3 times a week but cannot recall doing anything that would have caused injury.