Had to look up what the implications are of peroneal nerve damage, and I found that this is another way of saying foot drop. If that's what's happening with you and you can't use your foot, I'm stumped as to why it would be swollen. Swelling isn't really a part of MS.
I think your best bet would be to see your primary doctor and get to the bottom of this. Something else besides MS may be going on.
Good luck.
ess
The first thing I would suggest as a used to be nurse is to keep it elevated on a pillow or something to reduce swelling : )