That is Newtons first law, the conservation of energy but dare say one day it will be challenged.
But define what was created, our galaxy, Earth or the universe. If there truly was nothing, complete and absolute nothing then there would be nothing to go bang, nothing to make it go bang or anyone to start the big bang. So does this mean time never started, it must always have existed because the universe has always existed but then where did it start, maybe it never started because it was always there. If time has always existed along with the universe then there is no reason for us to run out of energy because it will always have been there and as it cannot be destroyed, therefore always existing and can only changing form so we just need to find ways of using it in all forms.
Regarding Newtonian physics, and Einsteins theories and quantum physics, there is a minority but growing band of scientists that are of the mind that these laws and theorems may only hold true for our galaxy,.
The problem I see with your energy analogy is that, given the that energy can be neither be created nor destroyed, this excludes the rest of the phrase of the theorem, which includes it can only have its state changed. That change of state may be to a form we as humans can not utilise. I liken it to photosynthesis in plants, if we could derive our bodily energy the same way, we would reduce reliance on fossil fuels, I think the nearest we have to it is photovoltaic energy, but we then turn this into electrical energy, which we use and then lose to another state, some being heat but where and what are the other states it changes to.?
Time? Is that not just a human invented measurement construct.
If you discount it, because it is an invention, then actual we are moving through space, it is because we visualise this movement as linear, we therfore assume there is something in front of us, hence everything we have done must be in the past. To conceptualise this into a structured format, mankind invented this into an artificial abstraction of a physical measurement and labelled it Time. Therefore time is not physical, like say gravity, its an imposed boundary, and as such mankind is stuck with the constrained view of past, present and future, which I see as analogous to needing a beginning a middle and an end. So the existence of everything, given by the trite but possibly accurate phrase of, it was, it is and always will be, this requires no beginning no middle no end, so just a simple answer could be "EXISTS" We label stuff like this as infinity, which is a construct we can not envisage, and a mathematical nightmare, destroying all possible results.
OK, off for some paracetamol for my headache ....