I Just Read That Nexplanon Was Effective Immediately Only If

I just read that nexplanon was effective immediately only if it's inserted between day 1 and 5 of your period, and any other time you have to use a backup method for 7 days. But I got mine inserted on the 18th of august and my period was from the 10th to the 15th or 16th of august. My doctor said I would be protected right away and so I had unprotected sex, should I be worried ?