Kayleigh, as PJ says, you do not need to be worrying that this lump might be cancer, but it could be some sort of infection. If you have read the links that PJ suggested, you know that breasts experience "growing pains" during puberty, so a sharp pain and some lumpiness can be perfectly normal. However, if your breasts have finished growing, this pain may need a doctor's attention. Let an adult know about this pain and help you decide if you need to see a doctor.
We hope you find this general health information helpful. Please note however, that this Q&A is meant to support not replace the professional medical advice you receive from your doctor. No information in the Answers above is intended to diagnose or treat any condition. The views expressed in the Answers above belong to the individuals who posted them and do not necessarily reflect the views of Remedy Health Media. Remedy Health Media does not review or edit content posted by our community members, but reserves the right to remove any material it deems inappropriate.