It is not unusual, particularly in young women to get a lump under the nipple which is mostly due to hormonal fluctuations.I don't think you should be worried too much since you are so young and also because pain is almost never associated with breast cancer.
Usually these lumps tend to get better on their own providing that the area around the nipple doesn't look red and swollen.
A cysts could appear most often during the two weeks before your period and resolve spontaneously after your period ends.
You could schedule an appointment with your physician and get yourself evaluated clinically if this lump persists.It could also be an injury,or an infective process that should be treated with antibiotics.
THANKYOU so much! It's been 3 days now and I've noticed the pain ihas slowly decreased especially when I wear a supporting bra! Thankyou again