Sore ankles from jogging?

i just started going to the gym today. id say im pretty unfit. i fast walked/ jogged between 3.5 to 5 mph for about 20 min on a treadmil and now my ankles are pretty sore. i have decent running shoes already, so what else can i do to prevent my ankles from being so sore? i had this problem in gym class when i was in high school too... it would last for days with no relief.