How Can Indented Stretch Marks Besides The Underarms Be Treated?

hi,i'm 22, 112.2 lbs, 5'2". my weight is fairly stable.. the sides of my underarms both have what appears like a stretch marks. its reddened but not painful. it appeared several months ago. i thought it will just fade away but it didn't. now i noticed that there's another small skin that's "separating". its not painful, but its indented. please help!!!