Medical expenses are deductible if they are to cure, treat or prevent a disease or condition that affects the natural function of the body. While purely cosmetic procedures are not deductible, it does not sound like this was really a cosmetic procedure.
You can deduct amounts actually paid to the provider in 2021 as 2021 expenses. For example, if you financed with a third party bank or credit card and the provider was fully paid, you can deduct the entire amount. If you financed with the provider and are paying your monthly payments to the provider, you can count what was actually paid to the provider.
