After you launched the game, minimize the game's window and open the task manager by pressing Ctrl+Shift+Esc
Click on "More details" down below the task manager if you never opened it, then click on "Details" and search for the Terraria.exe process, right click it and press on "Set affinity"
After that the "Processor affinity" window opens, and then you need to uncheck the first CPU, basically named "CPU 0", then close the task manager, and come back to your game, and try if that helped.

If it helped you, you're gonna have to uncheck the first core everytime you start the game, so keep that in mind. (there's programs that can automate that process, but i'm not that smart to do it so..)