security - Am I unsecure after adding untrusted PPA and installing software from it?

I needed to install Gemalto PKCS11 Library.
As a result of my searching, I added following PPA to my software sources: https://launchpad.net/~arnaud-morin/+archive/ubuntu/gemalto
Then I installed software package from it:
sudo apt-get install libgtop11dotnet*

However after reading following question I realized that I should probably not do that, because I don't know the author and the number of PPA users is quite limited:
Are PPAs safe to add to my system and what are some "red flags" to watch out for?

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According to the note on Launchpad, mentioned repository could be considered as untrusted:

You can update your system with unsupported packages from this untrusted PPA

Thus I am afraid that I open some vulnerability on my system.
Is it enough to just remove the untrusted PPA and sudo apt-get purge installed package? Will I be safe again or should I completely reinstall my system to be 100% sure that I am safe, that nobody will access my data?