Hello, i have a small bump under my left rib cage. i went to my primary physician and he said it was most likely a lymph node but it's gotten bigger. ?

Could be: Other possibilities include a benign fatty tumor called a lipoma or a cyst. Cancer is low on the list of possibilities in a young adult.

Biopsy the bump: any bump,that grows should be looked at again. It this is a lymph node your doc may want to,biopsy it to send to,pathology for evaluation. While this is most likely benign, you sound nervous and this way you can find out for certain.