I walk 2 miles every night and my left ankle to mid shin really aches. What is this and how can I make it stop?

Shin splints. Shin splints is the first thing that comes to mind. Proper stretching before and after exercising is helpful as well as icing the sore areas after a workout. If this is not helpful, i would see a doc and be evaluated. There is a more serious condition called a compartment syndrome that may be the cause.
Shin Splints. Best to support arch with orthotic. Ice after walking helps. Try to walk on a flat surface avoid hills.
Likely shin splints. This kind of exercise causes lots of stress on your bones. If your weight is in a good range, i would ask your family doctor to consider x-ray to look for stress lines of increased calcium. If they are there you mild want to alternate swimming with your walking to decrease this stress.