You will continue to develop for several more years. Just because you have some pubic hair and all doesn't mean you are done developing. The hormone levels in your body are high and it is common for a male to get puffy nipples. Remember, your muscle mass is going to increase as well - your body is changing and sometimes things "appear" funny but really aren't. You are NORMAL.
Puffy nipples and developing breasts (gynecomastia) are two different things.
You would need to see your doctor for an exam.
Hope it helps.