Have Medical Questions? Ask a Doctor Online!
This is Dr. David
I am sorry you have noticed your leg is going numb.
a movable lump in the lower left side of the back can be a benign lipoma fatty mass or a subaceous cyst
most likely that lump is not what is causing your numbness in your legs
you could be having a slipped disk or pinched nerves close to your spinal cord which is causing your left leg numbness.
poor circulation into the leg can also cause sometimes pain and numbness.
how old are you?
you may need to see your doctor to get your spine examined and you may benefit from a lower back MRI scan to check your nerves and bones and disks in your lower back to check for pinched nerves.
do you have any lower back pain?