I get it in my hands. Feels like a bad sunburn but inside. Was told it is part of fibro.

Maybe neuropathy?

I recommend going to urgent care, there they can take a X-ray right then and quickly get results. I was having severe pain in my right foot and I couldn't take the pain anymore. Come to find out, I have Achilles tendinitis, bone spurs in my heel as well the side of my foot. As well I have Really bad Osteoarthritis in my foot,left knee. Please get it checked. I've been on a medical leave since July. I have to wear a boot from the Dr. As well I have to get a special type of shoes.
I'm sorry I said so much, but again please go. The Dr. Will refer you to a Podiatrist.

Check out symptoms of plantar wart. You can't always see the wart, you may see a callus. It's painful to walk on. My podiatrist surgically removed mine years ago.

I am dealing with a similar issue - although I have mostly numbness (right heel) an occasional burning/pain. I have been to a podiatrist, am getting a nerve conduction test on the nerve that runs through the ankle. I will post what the results are. It seems to me it could be a minor injury that would not be too noticeable on someone else without fibromyalgia but because my body reads everything as amplified sensory reaction that maybe it is still a fibro related (but also with an underlying mechanical reason since it is only on one foot and has been persistent and unchanging unlike other fibro symptoms- which can last a while but for me anyway not permanently).