Over sparge?

Greetings everyone. New guy on the block here. I started a small batch BIAB gallon brew this morning. During the sparging, I may have added too much water. I adjusted the amount for the boil to about 1.5 gallons. In theory, I should have 1 gal when it’s finished. If I don’t however, and need to add to make the amount up to the gallon, can I use the leftover/out wort or just use clean water to make the correct amount for fermentation?

Thank you all for your time and advice!!

Either way, be sure to boil it for 10 or 15 minutes first. The wort will net you a higher gravity for the end product.