Bug Bite?
Peter paused to consider what might have caused this. He might have been bitten by a bug or had a parasite infection. Maybe he woke up in the middle of the night with a bug stuck to his thumb? However, he had never seen a parasite that acts in this manner. After researching it online, Peter came to the conclusion that no parasite could have caused this. Surely, the answer to his problem is much more serious.