Tough call. You say it’s tiny and clearly it was not part of your original composition, but based on the “difficulty” for the contest, it had better be nearly unnoticeable. There’s no harm in posting it and it getting pulled, though; it just means that you’ll have the opportunity to post another photo of something else!
/Just FYI, questions like this will get a better response if they’re asked in the thread specific to the contest.
//Also FYI, we appreciate it very much that you took the time to come in here and ask about something you weren’t sure about rather than just posting it! 🙂