"Hello, I am 19 years old and I have noticed that I have a dimple under my left breast when I raise my arm. This worries me."

It is important to pay attention to any changes in your body, especially if you notice any new or unusual marks or indentations. In this case, it would be advisable to schedule an appointment with a healthcare provider to have it checked out and to rule out any potential concerns. In general, if a mark or indentation is small, has a regular shape, and matches the color of your skin, it is less likely to be a cause for immediate concern. However, it is always better to err on the side of caution and have a healthcare provider assess the situation.