Lump in my left . Gynecomastia maybe?

Okay for 2 months now I've had a lump in my . I think it is diminishing in size now but what could it be? I heard it could be hormone imbalance onset by puberty which can cause gynecomastia but I found out more about lumps and I saw something about pseudo-gynecomastia and saw a picture and it looks exactly like what I have. I weigh 147 (I gained muscle weight) so I'm not overweight but I take a medicine called Risperdal and I heard that could cause it. So I'm confused what do I have?