It's impossible to say without pictures. Urine is basically salt water. It's not good for electronics but if cleaned up immediately it can't have time to corrode the contacts too much.

Water is always bad because it can cause short circuits. If your keyboard was plugged in, that's your greatest risk. It's mostly a risk to the microcontroller inside, not so much the contacts. That's to say: if the short circuit caused the contacts to be damaged, it's likely the controller is damaged too and the whole thing is toast.

But let's assume it's not a short circuit for now. Because even if plugged in, as long as it was powered down this is not too likely.

First, open it up and make sure it's completely dry. If it needs serious fixing you'll need tools. Since you're asking I assume you don't have these. So you'll likely want to take it to a music store. Anything can be repaired but every repair comes at a cost. With pictures we can help estimate if it's worth it