Imagine our univers we live in and know is a bubble. Now each time a decision is made, a new universe bubble is born.
You would just create another universe is all.
From Dr. Michio Kaku
Kaku: There are two basic obstacles to time travel. The first is energy. We need astronomical amounts of it, in either the form of positive or negative energy. At 10 to the 19 billion electron volts (a quadrillion times larger than that produced by our most powerful machine on Earth) space itself becomes unstable, and "holes" and bubbles (baby universes) begin to form out of the space-time "foam." At this energy, it may be possible to build a time machine out of the discontinuities in space-time. Also, there is the problem of stability. [Stephen] Hawking once thought that time travel was absolutely impossible because a law of physics prevented it. After that, counterexamples have been found, so the burden of proof has shifted. Now, it’s up to the cynics to prove that time travel is NOT possible. But there is one last problem: radiation. Once we quantize the wormhole, there is the possibility that high-intensity graviton radiation will fry anyone who enters the time machines. This is still an open question, although string theory should solve it.