I am pretty sure that the ant didn't fall into your penis. It may have fallen next to your penis and when you couldn't find it you thought it fell into your penis. Your pee hole on the head of your penis is not open enough for something to fall in there. If indeed something were to fall in there IE: an ant, you would have bigger problems than just an ant being in there. If you still think something is in there, and it didn't come out when you peed, then I would go see a urologist to see what the problem is..... as long as nothing is interfering with your ability to urinate I don't think you have anything to worry about. Good luck.