There are a few things you should be doing but don't expect instant results.
Make sure you have a healthy diet, cardiovascular exercise is a must and also do some heavy lifts.
Train your chest at least every 4 days to get the best results.
Hope this helped
This is a difficult one as you may be in the beginning stages of gynecomastia, and no amount of chest exercises will get rid of it. Since you brought up the term "man boobs", that tells me it's pronounced enough that it's noticeable. While it's not an uncommon occurrence, if treated quickly it can be reversed. However if left untreated, your only option is surgery. Definitely have a Dr look at this for you and don't put it off.