What Causes Purple Sunburn Patches On Thigh?

I HAVE A SUN BURN ON TOP OF MY THIGHS THAT ARE NOW TURNING PURPLE AND SPLOTCHY. MY SHOULDER ARE SUNBURN ALSO, BUT ARE FINE. I HAS BEEN A WEEK AND MY LEGS ARE STILL TENDER. I DO HAVE ISSUE WITH INFLAMATION(STILL WORKING WITH DR) SHOULD I BE CONCERN OR JUST WAIT.