Hopefully it was just your test vessel. If not, and that taste is in your beer, there's still a good chance it will mellow with age. Personally, I'd recommend you switch to Star San or Iodophor to sanitize. According to FDA standards, One Step no longer technically qualifies as a sanitizer. That's probably not what caused your off taste, though. I used to use One Step, and I never rinsed it. Assuming you diluted properly, One Step shouldn't cause off flavors.
If that strange soapy flavor does persist through your secondary (I don't think it will, and I hope it doesn't) it should mellow with age. You might have to just sit on that beer for a few months, but it should get better with age. Really the only two off flavors that aren't going to mellow out are from oxidation (cardboard) and infection (unwashed badger anus). Anything other than that, or just having a crappy recipe, should ease out over time.