Iphone 5c With Long Pink Spot

Hope it you can see it, but it takes up 1inches wide probably 3 inches tall of the screen.. all I know it can get hot, and it's battery died last December to a 2h30mins time span. I believed, because it got too hot, the battery drop pretty easy. It dropped easily while updating the apps, from 38% to 18%percent really quickly and it was hot. But I reseted it, and is currently re-testing the battery time. Which takes days. But this pink circle worries me. Is it broken?

This is refurbished from long time ago. Maybe almost a year. Even card claims 1 year warranty. :l Maybe I don't remember.