It may be a combination of factors.
Some discomfort MAY be withdrawal symptoms. Cigarettes have more addictive substances in them than the
tobacco and nicotine themselves and some people experience bad withdrawal from those. Some don't.
Another issue could be an allergic reaction either to PG, VG, the flavorings or, on extremely rare cases, all of the above.
Another thing that you should consider is that the detoxing process itself can, in some cases, temporarily lower your immune system, making you more susceptible to disease for a while.
As long as you don't feel it is anything of real concern (you know your own body better than any of us), you should be fine.