Brown discharge

I had my first child October 9th 2016. After having my child I bled for about three and a half weeks. Around December sometime I got the nexplanon implant. About a week after that I believe to have a normal period that lasted for a week and a half. Three days after ending the period I noticed Brown discharge that was accompanied buy a smell similar to the smell I had after giving birth. It does not itch or burn. And everything else is normal down there.

Any idea of what it could be and what I should do?