Small breast dimple no lump

Hey, 

I’m 22 years old and live a pretty healthy lifestyle (plant based diet, not overweight and never have been) and have noticed a tiny dimple on my left breast, on the side where your breast meets your ribcage  (which has naturally always been the bigger one) There’s no lump at all, and in all fairness I don’t think this ‘dimple’ is new, I just happened to notice and focus on it this evening. It is only noticeable to me when sitting normally with arms down, in any other position it completely goes. Again, it is extremely shallow and small. Would you say this is cause for concern or is this normal for some people? All the posts on the internet regarding breast dimples are very scary, so looking for reassurance more than anything. No family history at all of breast cancer. Any advice appreciated :)