en_tn/jhn/01/27.md

who comes after me

John is speaking about Jesus. The phrase "comes after me" means that John's ministry has already started and Jesus's ministry will start later.

me, the strap of whose sandal I am not worthy to untie

Untying sandals was the work of a slave or servant. These words are a metaphor for the most unpleasant work of a servant. Alternate translation: "me, whom I am not worthy to serve in even the most unpleasant way" or "me. I am not even worthy to untie the strap of his sandal" (See: rc://en/ta/man/jit/figs-metaphor)