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 care for a spreading infection accompanied by fever, confusion, faintness, severe weakness, or feeling seriously unwell.
These symptoms can indicate that infection is affecting more than the nail fold.
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
Seek urgent medical care if redness or swelling is spreading beyond the nail, pain is rapidly worsening, movement becomes difficult, or red streaks extend up the finger, toe, hand, or foot.
3
Does any of this apply?
Book an appointment
Arrange routine medical care if:
Pain, redness, or swelling is not improving
You can see or feel a pocket of pus
The condition keeps returning or lasts longer than six weeks
The nail becomes distorted, discolored, or separated
Several nails are affected
You have clear blisters rather than pus
You may have an ingrown toenail
You have diabetes, poor circulation, or weakened immune defenses
Every sign above is quoted from the sofidex article on Paronychia. If you are not sure, err upward — it is always reasonable to be checked.