Is it not showing up in the list of apps running when you go to Force Quit?
Open Activity Monitor (Applications > Utilities > Activity Monitor), look for Sims 4 in the list of processes running, click on it to highlight it then click on the grey X near the top left corner of the window. Follow the prompt to quit the process.
I think this was an issue a while ago but was resolved. What version of OS X are you running?
I have OS X Yosemite.
I tried, it didn't work :/
I even deleted and then downloaded the game again, still nothing
That's a pain. I'll try to find the other couple of threads people posted and see if any of them responded. I seem to remember it happened after a certain patch.
