If you notice your tank setup gurgling when you draw on it, it implies a flooded chamber. If you inhale hard enough, you could aspirate tiny drops of
e-liquid. It's really not a big deal, more of an annoyance than anything, but you want to vape your e-liquid, not drink it.
As to the toxic aspect, you will feel other effects before you get to a toxic level - nausea, dizziness, tremors, headache, and more. The toxic dose for nicotine (from a 2013 study) is 6.5 - 13 mg/kg orally. For a 150 lb (68 kg) person, that would be about 440 mg of nicotine at the low limit.
A "high" nicotine level e-liquid is 24 mg/ml. You'd have to
drink 18 ml of that e-liquid in one sitting to approach toxicity.