The Child Tax Credit is a non refundable credit, which means it reduces your tax liability (income you are taxed on). When you do your amended return, you may owe some money back because part of the child tax credit reduced your income you are taxed on, which in turn you received a refund.
You need to do the amended return because it would be hard for anyone here to tell you what or if you would owe money back to the IRS. If you end up owing, you should pay the amount as soon as possible because the amount owed will incur penalty & interest until it is paid in full.
