As a 副助詞（ふくじょし） (adverbial particle), ばかり usually has one of three basic meanings.
程度（ていど） - Highlights the ‘rough’ amount/degree of something (similar to くらい).
限定（げんてい） - Highlights the ‘limit’ of something (similar to だけ).
完了（かんりょう） - Highlights the ‘end’, or ‘completion’ of something.
In this lesson, we will focus primarily on the 完了（かんりょう） meaning. When connecting ばかり to the past form of a verb (using た), it will imply that a specific action has ‘just finished’, ‘just stopped’, or ‘just been completed’.

• 駅（えき）に着（つ）いたばかりに友達（ともだち）から「やっぱり今日（きょう）は遊（あそ）べない」とメッセージが来（き）た。
  Just as I got to the station, I got a message from my friend saying, ‘Actually, I can't hang out today’.
• 一回（いっかい）遅（おく）れたばかりで先生（せんせい）に怒（おこ）られた。
  I got scolded by my teacher for being late just once.
• さっき食（た）べたばかりだから、お腹（なか）はまだ空（す）いていない。
  I just ate earlier, so I am still not hungry.