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 prompt medical advice if the skin becomes increasingly red, warm, swollen, painful, or starts producing pus.
These may be signs of infection, particularly after injury or attempted home treatment.
Get urgent help if bleeding is heavy or does not stop after steady pressure with clean gauze.
This is unusual unless the tag has been cut or torn.
Sudden hearing loss, severe ear pain, or discharge from the ear canal should still be assessed promptly, although these symptoms are unlikely to be caused by an uncomplicated ear tag.
Arrange a routine appointment if an ear tag has not been assessed before, if you are considering removal, or if it repeatedly catches, bleeds, or becomes sore.
Review is also appropriate if there are concerns about hearing, speech development, ear shape, or other differences present from birth.
The article also says
The tag itself is not an emergency.
Every sign above is quoted from the sofidex article on Ear tag. If you are not sure, err upward — it is always reasonable to be checked.