Along with Pinkertinkle's questions, I'm also wondering HOW late were you? If we're talking a few minutes here, then I'd say no sweat. But if you were like 30 min or more, then I guess I might be concerned. If it's that bad, I'd send them a letter of interest, with a brief apology for your lateness. Don't overdo it here. Just let them know you acknowledge your tardiness and you're sorry. Two sentences max. But if you weren't that late I wouldn't draw any attention to it. It'll make it look worse then it was. Good luck.