Battery Health

Hi I have a question regarding my iPhone 13 pro battery health I bought my phone on April 2022 it's nine months now and my battery health has drained to 92% I don't know if my battery is faulty or I'm using my phone more but I am trying best first I use the original charger and I don't let my phone die due to charge and also try to charge my phone before it drops less than 20% and I have this question because one of my cousin bought iPhone 13 Pro same as me same variant and it's five months old and his battery on this still 100% what is the issue. I want to know that like if my battery is faulty or what because my cousin battery health is hundred percent and my battery health is at 92% if this keep on going like this I might have to change my battery in next 1 year which is not good. What I Can do to save my battery health apart from the tips given on the apple website and suggest if i should go and get my battery checked.