Indent over belly button, 1 day post op. Will this go away? (Photo)

This will almost certainly resolve with time. It is actually difficult to create a lasting indentation unless trying to. At this SUPER EARLY point after surgery you should not really be evaluating swelling/irregularities/asymmetries too much as these are common and typically temporary.

You are at the very beginning of your recovery.  You will experience many changes to the contour of your abdomen over the coming months.  You are swollen at this time, so an appearance such as this is not abnormal.  Try to relax and continue to follow the advice of your surgeon.

This is likely just a progressive tension suture which will resolve with time. Your surgeon will know for sure. Don't worry about it for now and just wait for your first follow up appointment. 

Thank you for your question and sorry to hear that you are worried so early in the process.  At 20 hours it is unlikely that something permanent has occurred.  Occasionally a bandage will slip and impress a "dent" or for some reason swelling in the surrounding tissue creates that appearance.  Once swelling resolves expect to see improvement if not reversal.  At this point just follow your surgeons instructions and recover.