Mouse pointer

If this is an issue you're having with only EU4 and other programs are working correctly, I'd suggest a reinstall, including deleting the files located in Documents\Paradox Interactive\Europa Universalis IV

If that still hasn't fixed anything, feel free to post on our technical support forum over at:
https://forum.paradoxplaza.com/forum/forums/euiv-technical-support.812/

Hopefully your issue gets resolved swiftly.