It should be fine, as long as you sanitized before puting the airloock back on. The CO2 blanket from a vigorous fermentation will provide a great deal of protection. Leave it in primary for a few weeks, but keep an eye out for infections (still unlikely if there were no other lapses in sanitation), look for things like mold on the surface of the beer or giant bubbles forming with a white spiderwebbing on the beer surface or a dramatic change to the nasty in the smell coming out of the airlock. Even if you see these signs though, your beer will most likely be salvagable, so don't panic , just post and listen to the advice you get. Also, what type of container are you using for fermentation? Try to maintain at least a gallon of headspace above the wort surface and eliminate the need for the blow off tube.