On may 25th i sliced the tip of my big toe open. it's healed completely, but still hurts horribly when i "stub" it & there's a numb lump under my toe?

Yikes.: The tips of toes, and fingers for that matter, just don't like to be sliced. They are typically a painful heal and the injured pain receptors will take many months to calm down completely. The numb lump is either part of the initial injury or secondary due to an altered gait. Either way, it too, will more that likely pass. I speak from experience.