I Have A Several Pain In My Right Buttock, About

I have a several pain in my right buttock, about the size of a saucer. Does not radiate to any other areas. Sometimes it is so painful that I am unable to walk because of pain. Even then, the pain stays in my buttock does not hurt in leg.
I have fibromyalgia, Sjogreen's Syndrome. The only med I take is Levothyroxine.
Thanks for any idea you might have.