Chin crease. How did these folds in my chin appear all of a sudden? (Photo)

The 2009 picture certainly shows the same chin crease but less pronounced. The crease is caused by muscle contraction and the more the muscle is used, the bigger it gets. You may consider Botox treatment to help atrophy it, but it may also effect your smile.

Thank you for your photos. Facial muscles and
structure change and develop as we age. You would likely benefit from a
small amount of Botox or filler injected into your chin to improve the area
that concerns you. I suggest seeking a consultation with a Board
Certified Facial Plastic Surgeon to discuss your concerns and see if you are a
good candidate for Botox or filler. Best of luck!

It might be related to your face being thinner than it was 6 or so years ago. Hard to say for sure without an exam.