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 for serious trouble breathing, throat or tongue swelling, fainting, or rapidly worsening wheezing.
These can be signs of a severe allergic reaction or another medical emergency rather than routine allergic rhinitis.
And for anyone, someone who:
Seek prompt medical assessment for persistent one-sided blockage, frequent nosebleeds, severe facial pain, high fever, swelling around an eye, vision changes, or a severe headache.
These symptoms are not typical of uncomplicated allergic rhinitis.
Arrange routine follow-up if symptoms remain bothersome after appropriate self-care, interfere with sleep or daily activities, or require frequent medicine use.
Follow-up is also appropriate if the diagnosis is uncertain, side effects occur, or asthma is not well controlled.
They may adjust the treatment approach, arrange allergy testing, or refer to an allergist or ear, nose, and throat specialist.
The article also says
A clinician can review whether the medicine is being used consistently and with the correct technique.
Every sign above is quoted from the sofidex article on Allergic rhinitis. If you are not sure, err upward — it is always reasonable to be checked.