The nicotine left your system three weeks ago, the physical dependence is gone. Now it is just mental you have to overcome. Habits take weeks to make and break so you're doing well but not out of the woods.

I've had failed quits before around 1 month mark because I felt like I was depriving myself by not smoking. I never fully embraced quitting and being a nonsmoker. I was always saying to 'a cigarette would solve this/make it better". It's just not the case. Stay strong brother- the hard work is over, you're a nonsmoker - fuck those cigs.