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 reduced vision, pain when moving the eye, difficulty moving the eye, a bulging eye, severe swelling around the eye, or severe illness.
These are not typical features of a simple chalazion and can occur with infection involving deeper tissues around the eye.
Arrange prompt medical assessment for a lump that:
Seek urgent same-day care for rapidly worsening redness or swelling, significant tenderness, pus-like drainage, or fever.
These symptoms may indicate an infection that needs treatment.
Routine follow-up is appropriate if a chalazion is not clearly improving after several weeks of consistent warm compresses, keeps returning, becomes large, or affects vision.
An appointment is also reasonable when the diagnosis is uncertain or eyelid inflammation occurs often.
The article also says
After an injection or surgical procedure, follow the eye specialist's instructions.
Contact the treating clinician if pain or swelling is worsening rather than settling, bleeding does not stop, or vision changes.
Every sign above is quoted from the sofidex article on Chalazion. If you are not sure, err upward — it is always reasonable to be checked.