I agree with Burnt. Niacin will only give you that warm fuzzy feeling

If you were testing negative when you smoked the bowl, you should again be able to test negative within 3 to 5 days of smoking. A one-time high on an otherwise THC free body should test negative in 3 to 5 days.

You should be okay, but just to be safe, get a home test and see. If you pass, don't overdilute on the day of the test.