Looking back with the knowledge base I've built up. I know bilateral pain often comes from SI Joint/lumbar spine being misaligned. If it's just one foot, often times the medial plantar nerve is adhesed. You will need a trained manual therapist to find this. I use Active Release Technique. But first start with the simple steps.
So here are a few treatment strategies. Roll your arch on a golf ball. This will help break up any adhesion's that may have developed in the muscle and ligament. Your body is all connected. Rolling the arch will actually even increase your hamstring flexibility! Do towel crunches with your toes. Pull the towel towards you using only your toes. This will strengthen your toe flexors. Stretch the calves religiously and roll your calves on a lacrosse or tennis ball. Remember your body is all connected. Try these strategies for 2 weeks. If your pain hasn't decreased substantially, find a soft tissue specialist. I see plantar foot pain all the time at our practice in downtown Grand Rapids. There is a lot of relief out there, go find it!