What Does "mild Disc Protrusion At L4-L5 Level" On MRI Mean?

i have been getting lot of lower back pain after a fall. the pain is worse if I bend over a little and if I sit on the floor. my legs start to go numb and my lower back gets very stiff. just got an mri and it says L4-s L5-s1 mild disc protrusion indenting the sac-- what does this mean and is there treatment