What Causes Numbness And Tingling Sensation In Forearm Radiating To Fingers?

I am 48 yr old female with family hx of CLL, hypothyroidism and skin cancer. For the past month, I have a heavy feeling in my left axilla and bicep which also begins to feel numb and tingles and extends to my forearm and thumb and index finger. I fractured a rib from coughing when I had left lobe pneumonia last fall. Any ideas what is causing this constant numbness and tingling which is unassociated with exertion or activity?