Suggest Treatment For Painful Lump Between The Breasts

Hi, I am a 17 years old and I have a bump in between my breasts. It is very painful, I have only just got this bump a few days ago. After I got the lump my nipples started hurting (getting very sharp pains) and getting really sensitive. I still go to school and do a lot of physical activities, and it is excruciating when I run, play sport and it only hurts a little bit when I am sitting. The pain feels like it s a stabbing pain. The pain goes through both breasts and the bump is continuously aching. Please help.