Newbie here! Question about ankle problem

[Siawa]

Not a first time runner, but first time in almost a year. I'm on week 7 on the C25K program and stumbled upon this site while proactively searching for what to do after I graduate!

I woke up before Run 2 in week 7 yesterday and almost didn't run because I felt something in ankle; felt like something was moving on the medial side of my heel as I flexed and extended, right below the ankle joint. Any idea what that is and is it serious?

I did do the run however and its better, but still there.