Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek emergency care for severe trouble breathing, inability to swallow saliva, rapidly increasing facial or throat swelling, uncontrolled bleeding, or a major facial injury.
Children with an underbite can be assessed before growth is complete, even if treatment is not started right away.
Seek a prompt medical appointment if your jaw or facial features are becoming more prominent during adulthood.
This is especially important if you also notice enlarging hands or feet, wider tooth spacing, headaches, heavy sweating, or changes in vision.
Contact your dental or surgical team promptly after jaw treatment if pain or swelling is getting worse rather than better, you develop a fever, the bite suddenly changes, or you cannot maintain fluid intake.
These symptoms need urgent attention regardless of your usual jaw shape.
Arrange a routine dental or orthodontic assessment if your teeth do not meet properly, chewing is difficult, teeth are wearing unevenly, or you are concerned about your jaw or facial growth.
The article also says
Stable prognathism is not an emergency.
Every sign above is quoted from the sofidex article on Prognathism. If you are not sure, err upward — it is always reasonable to be checked.