I have numbness in my left upper abdomen. No pain involved and I went to the doctor and he did a brief exam but said not to worry that it will go away?

Not satisfied? Your doctor has the benefit of having examined you--we of course cannot. If you feel a more thorough exam is warranted, or your doctor did not adequately address your concern, get another local opinion with a hands-on assessment.
Waiting in medicine. Your doctor is probably right. Numbness would most likely be caused by a swollen muscle or nerve or both from a minor injury. These usually resolve with time. Any further expensive testing will not likely lead to any more firm diagnosis. When we wait in medicine we are also waiting for other symptoms should something get worse. More symptoms often lead to more options for diagnosis and treatment.