It's day 4 after rhinoplasty. My ear cartilage has been used and it hurts. Does it grow again? Will there be consequences?

Your cartilage is a common donor when needed for rhinoplasty. Usually there are no significant aesthetic consequences but the cartilage will not regenerate.

The cartilage removed from your ear will not regenerate, but there are generally no adverse consequences of removing it. Pain is to be expected at the donor site, but will resolve over the next few days. If the ear is becoming increasingly painful rather than less painful, this can be a sign of infection or bleeding.  While uncommon, these are urgent matters which must be brought to your surgeon's attention right away.

The ear is a common donor area for cartilage and your surgeon removed some for grafting into your nose. This area is often painful although the pain subsides over a couple of weeks.  It is important that you let you surgeon know that you are having pain, however, since early complications such as a hematoma can occur and need to be treated promptly.As long as there is no complication then you should have no noticeable consequences.  But please do speak with you surgeon about the pain.  Good luck to you.