Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Seek emergency help now if you develop:
Trouble breathing or swallowing
Swelling of the tongue or throat
Fainting, collapse, or widespread hives
New or rapidly worsening weakness, difficulty walking, or breathing problems
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Contact a healthcare professional promptly if you develop an expanding rash, fever, severe headache, facial weakness, unusual muscle or joint pain, or a swollen joint in the days or weeks after a bite.
3
Does any of this apply?
Book an appointment
Routine advice is appropriate if a mouthpart fragment remains, the tick was very swollen with blood, you do not know how long it was attached, or you want to discuss whether preventive treatment is appropriate.
The article also says
Also seek advice if the bite becomes increasingly painful, hot, swollen, or begins draining pus.
These may be signs of a skin infection.
Every sign above is quoted from the sofidex article on Tick removal. If you are not sure, err upward — it is always reasonable to be checked.