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 immediately for trouble breathing, swelling of the face or throat, collapse, a seizure, severe confusion, or rapidly developing hives with breathing or circulation symptoms.
These may indicate a severe reaction requiring emergency care.
Seek urgent medical advice if you develop a high or persistent fever, repeated vomiting, unusual weakness, or a widespread rash, especially after a live vaccine.
Contact your healthcare team for routine advice if side effects are not improving as expected, are getting worse, or interfere significantly with eating, drinking, sleeping, or normal activity.
Also call if redness or swelling keeps spreading, or if you are concerned about a reaction not covered in your aftercare information.
Every sign above is quoted from the sofidex article on Vaccinations. If you are not sure, err upward — it is always reasonable to be checked.