What is this lump?

[Sammyspurs]

Hi all,
Christmas Eve I noticed this lump toward my armpit. it is only one side not the other.
when I push it in hard it feels gristly- when I gently press its soft- it is sore but I think that’s from all the prodding. No other symptoms. Any ideas? It’s above breast - side of arm pit kind of where breast meets armpit area Thank you

I think you probably know the answer is that you need to get booked in with a GP as the internet cant tell you. You will probably need it scanning in the first instance but they might advise you to wait a cycle (depending on your age) in case it’s hormonal and it disappears as quickly as it appeared.