Unprotected sex while on Nexplanon

I had sex three days ago, and yesterday Is when I noticed there was blood (light pink) in my underwear and when I wipe, and now there’s brown discharge.

The last time I had sex was a year. So I just became sexually active again, and I messed up by googling things. Also This is my second year of being on nexplanon. But has anyone ever experience anything like this.