Promissory note case

I gave some money to my friend's mother. Now she is not giving it back. When am asking the money she is threatening me, that she will suit a criminal case against me for doing illegal money lending buisness. I gave the money when she cried in front of me, telling her emergency. I have a blank promissory note signed by that lady and a blank cheque signed by her son. WHAT SHOULD I DO ... ?? PLEASE HELP ...