Here is a quick idea off the top of my head. Manually add loads to the surfaces of the threads to simulate the stress from the thread-lock. You will have to first find how much load it requires to deform them the same amount you already found in testing. Then, run your simulation.
In regards to finding out how much load to manually apply; I am not familiar enough with these types of simulations to describe the exact process, but I know there is a way in SW to add a sensor to detect the deformation. You run that simulation to increase the force until you get the deformation you measured in your tests.Then you will know how much force to apply to simulate the thread-lock.