I have a rough patch in between my breats

Hi!

I'm 15 and my skin started to get dark and rough in between my breasts like 2 years ago I think. But I got my period like 4 years ago so I dont know if its connected. Does this look like a serious problem? Sorry if this gets reported idk if its tmi

It's like rough compared to my normally smooth skin and it at first got to that dark shade before the texture went different. Is this normal? Should I be concerned? Like it's not my skin color at all I'm like a caramel tone everywhere else....