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 urgent or emergency care if a skin wound is accompanied by severe rapidly worsening pain, confusion, fainting, difficulty staying awake, or rapid breathing.
Arrange an appointment sooner if you have diabetes, reduced circulation, loss of sensation, or a weakened immune system, particularly if the skin is open.
Contact a healthcare professional promptly if you notice:
Routine medical follow-up is reasonable if the area is not clearly improving after several days of careful home care, keeps returning, or interferes with normal movement.
These are not expected features of routine chafing and may indicate a serious illness.
The article also says
After healing, return to the activity gradually.
If symptoms recur in the same place, review clothing fit, moisture control, equipment position, and barrier use.
Persistent or unexplained rashes should be examined rather than repeatedly treated as simple chafing.
Every sign above is quoted from the sofidex article on Chafing. If you are not sure, err upward — it is always reasonable to be checked.