The temperature that you steep the grains isn't very critical. Even if you boil them it probably didn't hurt although I wouldn't recommend that as standard practice. I think that the reason that it is suggested that you steep at 150 to 160 is to prepare you should you decide later to go to all grain brewing. The enzymes that cause the starches to be broken down into sugars that can be fermented are active in roughly that range.
For now, bring the water up to 160 or so, turn the heat off and let the grains steep. It will be fine. If your water is highly alkaline and you get the water hotter than 170 you can extract tannins but most water isn't that alkaline.