Did your doctor recommend any stretches ? If not, there are some good stretches for the bottom of your feet that can help. Another thing you can do is take a can of soda. Put it in the freezer. When it's cold, roll the bottom of your foot with the can. That can help reduce the inflammation. www.sportsinjuryclinic.net/sport-injuries/
As far as exercises, the pool or a recumbent cycle would be two good options. The recumbent cycle is one where you peddle in a reclined position. That takes stress off the foot or joints.
And you may want to consider getting a second opinion on your foot. Ask your doctor for a referral to a podiatrist. Physical therapy might be another option.