How do I fix the broken string on my blinds?

The cord (to pull the blinds up & down) snapped on my blinds. The cord was comprised of 2 strings with a small plastic piece at the end. While I was letting my blinds down the cord snapped & 1 of the strings went up into the top part of the blinds (which is covered by plastic). Is there anyway to fix this? Currently my blind is in the down position but I am unable to pull the blind up. Your help is greatly appreciated. Thank you.