Extreme Dent/ Muscle Deformation in left breast 6 months post op. What's going on?

Hello, I am six months post op from my breast augmentation. 415 cc moderate high gummy bear implants submuscular and inserted through the nipple. I started noticing an extreme dent forming in my left breast, but this wasn't the case until I started weightlifting again. My surgeon says that it's my old crease that hasn't stretched and that wearing a super tight bra will possibly help it shift back? Does that sound normal? Should I stop doing upper body to fix this? What's going on??