Heel spur. Heel spurs can cause that type of pain as can plantar fasciitis sometimes.
Plantar fasciitis. Try some shoe inserts like 'walk-fit" from target daytime and then a night splint to stretch it out at night and help resolve problem. At times we inject the sore area with steroids to get faster and longer term relief. Surgery is last option if the others don't fix it. Expect the inserts and splints to take 3-4 months to resolve this.