Depending on the nature / source of this charge you may find TCAD tools capable, or not.
Guardrings have multiple uses. They can capture or shunt substrate minority carriers before they wander into the core of a device (or out). They can inhibit field inversion that makes interdevice leakage when charge is trapped in oxide above. The former is handled better by device 2D/3D simulators (basic fields and physics) than the latter - for carriers in bulk Si you just have to get the mesh and the injection / initial distribution, while MOS effects depend on data fitting as response is highly process-variable.
You can use standard TCAD tools - but the problem is a huge size of the area to be simulated, huge mesh size, large memory and simulation time.
There were commercial EDA tools to simulate minority carrier injection effects, but non of them got a good traction with the industry, and I believe none of them are still alive.