Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services now if the person:
Begin emergency first aid if advised by the emergency dispatcher.
Emergency care may still be needed if symptoms develop.
And for anyone, someone who:
Contact a poison information service immediately after a child swallows or may have swallowed nicotine.
Do the same after exposure to concentrated liquid, an unknown amount, or any exposure causing vomiting, dizziness, shaking, confusion, weakness, or heartbeat changes.
Do not wait for severe symptoms.
For skin or eye exposure, start rinsing straight away and call for advice.
Routine follow-up should not replace urgent poison advice for a recent exposure.
Routine follow-up is appropriate after recovery if symptoms linger, exposure has happened more than once, or you want help changing nicotine use.
The article also says
Place an unconscious but breathing person on their side if you can do so safely.
Do not put anything in their mouth.
Every sign above is quoted from the sofidex article on Nicotine poisoning. If you are not sure, err upward — it is always reasonable to be checked.