not risky at all ,
nothing wrong with what you did mate ive done it loads of times
as long as you put a fully cycled filter onto the tank then you will not have any problems
the nitrifying bacteria needed is found mainly in your filter media, so using 100% tap water (dechlorinated of course) would have been fine as long as its the right temperature.... the nitrifying bacteria isn't free floating in the water so using old tank water isnt really needed