How long until nicotine is out of your system?

Bob W asked:

I quit smoking years ago by using nicotine chewing gum. Unfortunately, I got addicted to the gum instead. I chewed the gum for years. Three weeks ago, I went cold turkey and stopped using the gum. It wasn’t as hard as I thought. After a couple of days, I was fine. Until yesterday.

Suddenly, I am having terrible nicotine fits, three weeks after having last ingested nicotine. Is it all psychological, or could the nicotine have lingered in my body this long?

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