My boyfriend finished inside of me the day before I got Nexplanon taken out.

I’m desperate for a answer, I’ve had the Nexplanon 3 times i am a 20 yr old female im well aware with how it works however this time was a little different i had it inserted during my period as the doctor requested i had my period early December but got it again late December on 12/28/2021 once i got my implant my period completely stopped the next day. (Little background) After my second one i decided to take a break was on the pill but stopped almost a year later i just now got back on the Nexplanon again on 12/29/2021. On 01/01/2022 me and my boyfriend had unprotected sex which resulted with him finishing in me we assumed it’ll be okay since my doctor said
i got it inserted during my period i’ll be protected automatically, im just a little worried if i should be concerned about getting pregnant i’ve never done this before

Yes, there is a possibility of pregnancy. You'd have had to keep your implant in, for 5 days after intercourse, to gain your usual protection. That's the usual amount of time recommended.