Questions & Answers about Χτύπησα τον αγκώνα μου στην πόρτα και τώρα πονάει λίγο.
Χτύπησα is the aorist of χτυπάω / χτυπώ, so it means I hit / I banged in the sense of a single completed action.
Greek often drops subject pronouns when they are clear from the verb ending. Here, the ending -σα already tells you the subject is I, so εγώ is not needed.
Not necessarily. In this kind of sentence, χτύπησα τον αγκώνα μου στην πόρτα usually means I banged my elbow on the door, very often accidentally.
So although χτυπάω can mean hit/strike, in everyday contexts with body parts it often has the natural English sense of bang or knock.