I have a bump on the bottom of my foot? What should I do?

Have it inspected. By a doctor. Lumps and bumps should be biopsied. This is the definitive diagnosis of such lesions.
More information. Where on bottom? Is it under skin or on skin? Can you provide a description?
Could be. Many things. Not enough information.
Any lump. Or bump needs to be evaluated by a professional. Often times a biopsy is mandated to determine if the lesion in question is benign or malignant. (dangerous or not.).