help asap. Broken cast ?!

Hi; well about 2 weeks ago i got a cast put on my leg (foot up to knee) its a walking cast so i have a boot/shoe looking thing to wear with it. on the heal area, its starting to crack, now there is kinda a hole there, a few more days and im positive the remaining parts of where its cracked will fall off and there will be a hole. Iknow its kinda confusing but idk if i should go to the dr, and get a new cast put on. I sill have to wear it for 3 more weeks ! Helpp what should i do ? :/