I let my friend borrow $200 for rent she gave me a bad personal check what should I do?

I let my friend borrow 200 dollars to help pay rent and she gave me a personal check written out for $225 which was marked for a later date. The time came and I went to cash the check and there were no funds in the account. I had her and her boyfriend sign a promissory note and had us sign it. He got his check today and I still haven't received a penny of what I loaned them and they are avoiding me making up lies. What makes it worse is the friend is my ex and I did this out the kindness of my heart, What should I do all they do is text me excuse after excuse and wont answer my phone call. Thanks for the help