If the many-worlds interpretation of quantum mechanics is true, it implies that everything that can happen will happen - or has already happened. If time travel is possible, this would include every possible outcome of you traveling to the past and altering events.

What I think would happen is that nothing would change in this timeline. Instead, you’d simply travel to another timeline where you made those changes, and you’d experience the consequences of your actions there. However, it’s also possible that such a scenario doesn’t align with the laws of physics, meaning that nothing would happen because time travel to the past - and any related interference - might simply be impossible.