According to the theory of relativity, as described by Albert Einstein, the speed of light in a vacuum (denoted by 'c') is an absolute speed limit in the universe. In other words, nothing with mass can travel at or exceed the speed of light.
If you were moving at the speed of light, it would violate the fundamental principles of relativity. According to the theory, as an object with mass approaches the speed of light, its relativistic mass increases, and the energy required to further accelerate it also increases. As the object approaches the speed of light, its relativistic mass becomes infinitely large, requiring an infinite amount of energy to reach or exceed the speed of light. This is why it is not possible for anything with mass to reach or surpass the speed of light.
Therefore, if you were moving at the speed of light and threw a stone in front of you, the stone's speed would still be limited by the speed of light. The stone cannot exceed or even reach the speed of light relative to you or any other observer.