Hello and Welcome to MedHelp.
Any indentation in the breast is important to have evaluated. I'm glad you have no other findings such as lumps or pain but investigation to the dimpling/indentation is important. There are different reasons for why that can happen that are not serious in any way but because it is also associated with breast cancer, it has to be ruled out. When was your last mammography?
Here is some information on self breast exam https://www.emedicinehealth.com/breast_self-exam/article_em.htm#how_to_perform_a_breast_self-exam
Do you have an ob/gyn that you can give a call or even your primary care provider?