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 if erection problems occur with chest pain, severe breathlessness, fainting, or other possible signs of a heart emergency.
Go to an emergency department for an erection lasting more than four hours, including one caused by ED medicine.
Seek prompt medical advice if ED begins suddenly after pelvic or genital trauma, or occurs with new weakness, numbness, or problems controlling your bladder or bowel.
Do not wait for it to settle.
Sudden loss of vision or hearing after taking an ED medicine also needs urgent medical assessment.
Arrange a routine appointment if erection problems keep happening, cause distress, or affect your relationship.
Seek assessment for reduced desire, penile pain or curvature, symptoms of low testosterone, or a new problem after surgery or injury.
Every sign above is quoted from the sofidex article on Erectile dysfunction. If you are not sure, err upward — it is always reasonable to be checked.