Life happens. And sometimes we all make mistakes. If we are lucky a spotlight does not get shone on our mistakes but in some professions it does, and I think for good reason. However, the further distance what is basically a youthful mistake (with no severe consequences) gets the easier it will be to be menitioned and passed over. I appreciate how worried you are (anyone would be in a similar situation) but interviewers don't dismiss applications out of hand and without considering eveything. You did something dumb but hopefully the consequences will be less than you dread.