Unless you have pushed your commit to remote, you can always undo your last commit, you can try a couple different options:
From this stack overflow answer :
Reset and unstage all changes of last commit (so all files appear under
Untracked Files):
git reset HEAD~
Reset and keep previously added files staged (so all files previously
selected show under Changes to be committed)
git reset --soft HEAD~
Make changes to your files
Stage your changes
git add -A
Don’t forget to make a commit
git commit -m "my awesome commit message"