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 toes below a cast become blue, very pale, cold, severely swollen, or difficult to move, or if there is severe and increasing pain.
These signs can mean that circulation or nerves are under pressure.
If your child is wearing a cast or brace, contact the treating service promptly for increasing swelling, persistent rubbing, broken skin, a foul smell, drainage, or a cast that is wet, cracked, or slipping.
Arrange a routine appointment if you notice that a baby's forefoot curves inward.
This is not usually urgent, but an examination can confirm the type of foot shape and check how flexible it is.
The article also says
Seek an earlier assessment if:
The foot is stiff and cannot be gently moved toward straight
The heel also appears turned inward or downward
One leg or foot moves much less than the other
The curve becomes more noticeable rather than improving
An older child has pain, calluses, shoe problems, or difficulty walking
Every sign above is quoted from the sofidex article on Metatarsus adductus. If you are not sure, err upward — it is always reasonable to be checked.