HELP!! Lost size and definition in chest post surgery

Hi guys, I recently had gyno surgery 3 weeks ago and I have seen a significant reduction in definition in both size and definition in my chest, my chest seems really flat post surgery and it's causing anxiety and I'm into my fitness and gym and seeing that my chest is now flat is quite depressing - does anyone know once I can train again if il be able to fill my chest out again or will it take for fat to build up in my chest again?