I'm 13 years old, I honestly want to know if this could be a cause of growing because it has been hurting under my left breast

It wasn't REALLY bad pain but it just hurts and i want to know if this could be a part of growing and puberty, and PLEASE do not start automatically saying I could have a disease or something like that I have already worried enough about my health and don't need to anymore. All I want to know is if it is normal since I am growing and so on

Thank you :)