Pain in boobs

Not sure if this is the right room to be posting this in but oh well..

I’m 14 and about 4 days ago I just got off my period. 2 days later I noticed this lump in my left boob that was super painful and firm. I was concerned that it was breast cancer but then I had the thought that maybe my breasts are just growing. My left boob is now super red and swollen and it hurts pretty bad to the touch. The lump is still there. It’s only been two days with it and my right boob is completely normal. Help?!!!