The numbness and tingling in your left hand is more likely from a pinched nerve such as carpal tunnel, or a pinched nerve higher up. A brain tumor is less likely and would be accompanied by other symptoms such as headaches, nausea, vomiting, gait disturbances, vision disturbances, etc. I understand that you are inbetween benefits, so I therefore recommend that you buy a wrist splint and wear it to see if it helps. When you are able to see a doctor please do. If you develop other symptoms or if your symptoms worsen then you should see a doctor sooner.
If you have any additional questions, please ask. If no further questions, please click accept.