Lump between armpit and boob

Shaunna • 19

I've found lump this morning which I only noticed as it's painful when I move or touch it. It's about half a cm and is firm. It's not solid but it's not squashy. It doesn't stick out above the skin line. I have an appointment booked but closest is two weeks. Wondered if anyone could shed some light as I am worrying?

Thanks! Shaunna