If you have pushed the commit to remote and then erroneously amended changes to that commit this will fix your problem.
Issue a git log to find the SHA before the commit. (this assumes remote is named origin). Now issue these command using that SHA.
git reset --soft <SHA BEFORE THE AMMEND>
#you now see all the changes in the commit and the amend undone
#save ALL the changes to the stash
git stash
git pull origin <your-branch> --ff-only
#if you issue git log you can see that you have the commit you didn't want to amend
git stash pop
#git status reveals only the changes you incorrectly amended
#now you can create your new unamended commit