Lump under arm pit

Jen • Mommy to a 7 year old boy and 4 month old twin boys!
Hey ladies, I'm hoping someone here can give me some piece of mind! I found a pea sized lump under my arm pit on Sunday and am so scared. I have an 8 year old and 9 month old twins and have so much anxiety that I won't be around for them. I'm going to get it checked today but was hoping one of you have gone through something similar and can give me some reassurance that I'm over reacting and it could be nothing.