Will lifting weights help get rid of an indented sternum ?

Sorry but no: Your sternum is where your chest muscles (pectorals) attach but there's no muscle there per se to increase w/exercise. If the appearance really bothers you, talk to a thoracic surgeon but unless it's causing you medical problems, it's unlikely s/he will recommend any surgery, and even less likely that insurance will cover this cosmetic procedure.Try to focus on all your other accomplishments!