Because biopsy means sticking a needle through the tissue and pulling a piece of it out. It's better not to aggravate such lumps unless absolutely neccessary. Biopsy is a final stage in diagnosis.
do u know what they are gonna do next depending on what they find
I don't know exactly what they're gonna do next. Like you said, depends on what they think it is, and what you let them do. I only know for sure that anything cancerous gets diagnosed ultimately by biopsy, reason being that they won't start treatment unless 100% certain.
How big is the lump? How long have you had it? Is it growing? Is it painful? Sometimes, just sometimes, the body resolves these things by itself. Low lymphocyte count could be a problem.