Well, the numbness of my left thumb is still here. Its been more than a week.

The "numbness-hardened cement sensation" is not in the whole thumb, its only at the back of the palm side (sorry, I dont know how to describe the area). The strange thing is even if its numb, its painful when it touches something.
I know somebody online, she was taking ethambutol, she had the same odd sensations on 2-3 fingers. She stopped ethambutol because of optic neuritis. When she was off ethambutol, her odd sensations disappeared.

I am not sure if this is part of my previous/current nerve problems or due to ethambutol. Beats me!