Go to CVS and get the THC at home kit. Read the directions carefully, and then read them again. Use the urine from your first void (pee) of the day to take the test. You should see one control line and one line that indicates the test result. If you see any sort of line in the result indicator you have no detectable THC in your system.

Having said all of that, generally, one hit off of a babbit blunt will not cause a clean person to test dirty.