SimVision uses its own copy of Tcl/Tk which is installed inside the Incisive package. You do not need to install your own version, and indeed your local install won't be used even if you do, as the tools carefully pick up the Cadence-provided version (anything else would be a support nightmare).
Looking at the error message you get, I suspect the problem is with your Tcl code, perhaps failing to interpret a variable properly. However I see you tried to invoke tk_getOpenFile from the ncsim prompt; this is most likely a mistake. NCsim itself doesn't have Tk built-in, instead the Tk GUI features are provided via the SimVision prompt (SimVision runs as a separate process from the simulator).
At the bottom of the simulator's Console window you'll find at least the tabs "SimVision" and "Simulator"; switch to the SimVision tab to type any GUI commands.