I have a bright red spot on my lower leg i noticed two days ago and i'm getting a numb feeling in the back of my knee?

I'm not sure we can: put these two things together. The red spot is MOST likely a skin condition: eczema, psoriasis, etc. but another cause is allergies, perhaps to a bug bite. Have you been in a tick area? I suppose you must consider Lyme Disease, though this is much less common than many people think. I think the spot and numbness can both be watched; if the spots enlarge/spread or numbness persists, see your Doctor