What Does It Mean If I Have A Lump Underneath My Nipple?

No, Guys.
Its part of the growth process.
You are starting to grow your breasts.
There's nothing to worry about. Its all normal :)
Don't worry, Its okay.
When I was 11, That was exactly happened to me. My chest used to be FLAT. But I felt a lump. I was scared and worried.
But its okay.

Good luck :)

I have one 2 but I'm a girl its nothing to be super concerned but get it checked out just in case

It means you need to seek a physicians assistance in determining your problem.  This could be serious.  Please see your doctor.  It could be as simple as a stopped up milk gland or it could be something much more life threatening or somewhere in between.  Only a doctor can tell you for sure.  Don't delay.