Why is my chest concave 3 1/2 years post op and what can I do about it?

[Dub]

Hi,

I had surgery in March 2007. My chest is concave since. My chest goes into a crator around the nipple.

Is this because too much lipo was done or too much gland was taken out?

What can I do about it? Is it just a case of working on my pecs in the gym?

Pics are here https://www.gynecomastia.org/smf/index.php?topic=9297.msg112023#msg112023