It sounds like MS to me. I don't want to alarm you, but feeling like the following has been my foot experiences:
Numb on the bottom - like walking on pillows
Isolated numbness - like your sock is bunched up but it isn't and feeling
like your toes are taped together
Feeling like there is a "bar" between your toes and the ball of your foot
Lots and lots of tingling and pain almost anywhere on the foot at a given
I give you this information about my experience with foot tingling and numbness only. Knowing whether or not one lesion is responsible or not is not something I would imagine anyone could tell you. Plus, what happens to one does not necessarily happen to another with MS. I have heard of people with major disability with only a few lesions. Conversely I have heard of people riddled with them who have very little disability. One thing that our Tovaxin superhero Tim has always advocated is the four day rule. Since there are so many transient things/symptoms that can happen, I use his simple rule. If you get a numb area or lose some ability, wait four days. If it goes away, ignore it like it never happened. If is stays, it's probably a new symptom that may or may not go away with remission.
I caution you in reacting to things that last for less than four days. I literally drove myself nuts for about 3 weeks until I started using that rule. There are just so many things that come and go with the good and bad day thing that it would be like chasing your tail to give all of them any energy.
As for whether or not the LP could be the culprit, I have no idea. I would imagine that LP's could cause nerve issues since there is a breach of the CNS to get the fluid out, but I didn't personally have any. I just re read this post and I don't think I can really answer your question about the brain lesion with any degree of expertise at all. I can just tell you that the LP didn't "stir anything up" for me, but I do have lots and lots of tingling and numbness issues on my feet from the MS.