Breast indentation - early 20's

Hi, I’m 22 and have recently spotted a small indentation on bottom on right breast when I lift up my arm. My mum checked it out and I contacted my doctor asap. The doctor saw the indentation straight away when arm was lifted. However, she did not feel any lumps around breast area (both breasts). She has told me to let my period come and contact her in 3/4 weeks for another check up. Waiting for the next few weeks is causing a bit of anxiety. My mum’s mum has had breast cancer in the past. 

I was just wondering if there is anyone who had a similar situation around the age of 20-30?

Thank you