.gitignore and the following untracked working tree files would be overwritten by checkout

So I added a folder to my .gitignore file.

Once I do a git status it tells me

# On branch latest
nothing to commit (working directory clean)

However, when I try to change branches I get the following:

My-MacBook-Pro:webapp marcamillion$ git checkout develop
error: The following untracked working tree files would be overwritten by checkout:
.......
Please move or remove them before you can switch branches.
Aborting

This is what my .gitignore file looks like:

.bundle
.DS_Store
db/*.sqlite3
log/*.log
tmp/**/*
public/system/images/*
public/system/avatars/*

How do I get this working so I can switch branches without deleting those files?

If I make a change, will it affect those files? In other words, if I came back to this branch afterward would everything be perfect as up to my latest commit?

I don't want to lose those files, I just don't want them tracked.