Don't be concerned about keloids. You're probably not going to get them - if you were prone, you'd already know.
Don't fiddle with it. You need well fitting jewellery as if it's too long it's more likely to move or get bashed which means it's more likely to have problems. Too short is also bad, though. Be careful when brushing or washing your hair, and be really careful getting a haircut - make sure you tell them to avoid it, but it's probably best not to go for a while.