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
Go to an emergency department now if:
An erection lasts four hours or longer, even if it is not painful
The penis bent forcefully during an erection, especially with a pop, sudden pain, bruising, swelling, or loss of the erection
A retracted foreskin is trapped behind the head and cannot be moved forward
There is severe injury, uncontrolled bleeding, or rapidly increasing swelling
Penis or groin pain occurs with sudden, severe testicle pain
These problems can damage tissue if treatment is delayed.
Do not try to drain an erection, straighten an injured penis, or force a trapped foreskin into place.
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 same-day medical care if you cannot pass urine, or if pain comes with fever, pus, spreading redness, marked swelling, or feeling seriously unwell.
And for anyone, someone who:
has abdominal pain that is severe, constant, or getting worse
3
Does any of this apply?
Book an appointment
Book a routine appointment with a doctor or sexual health clinic if the pain lasts more than a few days, keeps returning, or is linked to urination, erections, or ejaculation.
Arrange testing if you have discharge, sores, a new sexual partner, or possible STI exposure.
A persistent lump, curve, wound, or skin change should also be checked.
Every sign above is quoted from the sofidex article on Penis pain. If you are not sure, err upward — it is always reasonable to be checked.