What Causes Feeling Of Sunburn In Upper Back?

Hello, So for the past 3 days I have this weird sensation of sunburn in my upper back. I really don t know what to think of it, it happened together with a flu, seems like I have recovered from the flu, but the sensation is still there. I wouldn t say it s painful or anything, but the skin is sensitive at the back and front (upper body part), I believe it might have to do something with anxiety, it s not bad, but I am person that tends to worry quiet a bit for no reason sometimes, specially at night before sleep, what could this be?