Aching off & on with pain in left leg by knee. alsoo noticed tiny bump. what could be wrong?

Where is the bump?: And tiny means a whole lot os things. Knee pain is often from arthritis or effusion or inflammation. It could be a tear inside your knee. It could be a stress fracture. A lump can be a mass. I think with all these findings a visit to your doctor would help clarify things. You can be examined and you can have an xray or MRI for further eval.