Pain in armpit down to arm

Hi,

 

I was wondering if any of you have had pain in you left armpit and slightly down your arm, I have had the odd breast pain but nothing unusual for me. I am 24 and am awaiting a mammogram for it, I have only experienced the pain for a week but my GP wanted to be sure as my aunty had breast cancer so it's more precautionary. I was just wondering if anyone else has experienced these symptoms and it turned out to be nothing? Any information would be greatly appreciated. 
 

all the best

sarah x