Hi claire,
First, seek medical help right away. You don't want to lose your foot, literally, over this.
Second, what kind of waiver does the doctor want you to sign? Normally doctors can't require you to sign away your right to sue them. This is a matter of public policy so it doesn't matter what type or how many contracts the doctor can create, that can't force you to not to sue them.
Please see a personal injury attorney for legal advice. Best of luck.
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