When I brewed extract / partial mash I used to top off with water straight from my tap. Probably 3 of 5 gals were straight tap water. I never had a skunky / sour batch.
I also used to start a syphon with my mouth and once I dropped my thermometer into the batch after cooling and stuck my hand in to grab it. That batch was good.
There really isn't anything alive in most city water anyway...
In short, relax 99% chance its ok.