I'm not a regular smoker but i smoked the other day. will the nicotine show up in my nicotine blood test a week from now?

If you are being: Tested, and you know you are being tested, then why would you smoke a cigarette? Most insurance companies and others who test for nicotine use urine rather than blood, but in any case a single cigarette would give you metabolites in blood for a handful of hours, and at most a day. You need to look at your impulsivity and judgment if you get tested regularly and still do it. Counseling might help.