Can I use retin a (tretinoin) on belly button rejection scar? Took the ring out 3 months old and almost closed. Scar isn't changing. Will retin a (tretinoin) help?

No. Retin a (tretinoin) type medications are really for the treatment of acne. For scars it is best to avoid sun, so use sunscreen or keep the scar covered. You can try some of the over the counter scar cream or vitamin e cream. There is some evidence that it could help. Scarring does take time and it can take many months to see how the scar will mature. They are red at first and turn white later.