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 after an injury if you develop:
New loss of bladder or bowel control
Inability to pass urine with numbness around the groin or anus
New leg weakness, severe numbness, or difficulty walking
Heavy bleeding, fainting, or signs of a major pelvic injury
These symptoms are not typical of a simple coccyx injury and may indicate damage to nerves, the spine, pelvis, or internal organs.
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
Arrange urgent medical assessment if there is an open wound, spreading redness, drainage, fever, rapidly worsening pain, or severe swelling.
You should also be assessed promptly after a high-force accident or if you have weak bones and significant pain after a fall.
3
Does any of this apply?
Book an appointment
Routine medical follow-up is appropriate if the pain prevents usual activities, is not beginning to improve after a few weeks, repeatedly returns, or has no clear injury behind it.
Night pain, unexplained weight loss, or a history of cancer also warrants medical review.
Every sign above is quoted from the sofidex article on Tailbone trauma. If you are not sure, err upward — it is always reasonable to be checked.