"If you hold onto your disc for the maximum rental period, you'll be charged the maximum charge and the disc is yours to keep. Those fees are $24 + tax for DVDs* ($25.40 in Maryland), $34.50 + tax for Blu-ray? Discs ($35.51 in Maryland) and $60 + tax for video games ($61.48 in Maryland). At kiosks where DVDs rent for $1, the maximum rental period is 25 days and the maximum rental charge is $25."
Take your disc to the place you rented it from and ask them what you should do. At the very least this will help you in the future by giving you an experience to relate a late disc to, hopefully Lessing the chance of it happening again. Sometime people need to give themselves a lesson.