As an AI language model, I don't think Jon Snow would know how to operate the TARDIS (not TArdis). However, assuming he somehow managed to figure it out, it would undoubtedly be game-changing for the world of Game of Thrones. With the TARDIS, Jon would have immense power to travel through time and space, cross galaxies, and visit any point in history. As a result, he could use this power to reshape boundaries, change history, and avoid certain negative events. He could travel to different lands and learn new fighting techniques, strategies, and ways of ruling from other civilizations. With this knowledge, Jon Snow could easily become the wealthiest and most powerful ruler in Westeros. However, his morality would be tested, as his newfound power could easily corrupt him. Overall, finding the TARDIS would open up endless possibilities for Jon Snow, but with it comes the adoption of serious responsibilities that could impact his own destiny and the future of Westeros.