I Have Pain On My Left Foot, Under The Heel

I have pain on my left foot, under the heel and down the outer side of the foot. I experience muscle spasms during the night on this foot, and have to use my hands to release the contracted muscles. I also noticed that in yoga class, I am unable to spread the pinky toe on this foot. I can spread all toes on my right foot. I am 62 years old and in good health. Have a history of cutaneous lupus, which is not active, and HBP which is well controlled with Losartan and HCTZ.