Most important is whether the partnership firm was registered under the provisions of Partnershi Act or no, where in your husband was a partner. Mere signing an agreement does not contemplate that the dues are clear, unless there is proper document executed which is of incoming and out going partner and likewise once again the said document is presented with the Office of Registrar of Partnership as it amounts to change in the constitution of partnership firm.
Kindly check the same and as you said you have got a cheque which has been issued to you by one of the partners which is still lying in your custody, present the same immediatly.
Pls note that where a person who is a partner in a partnership firm if retires at Will and leaves the partnership, the account so settled, the amount is payable from the account of the firm and not a personal cheque.
It having so happened, pls check with the Office of Registrar and with your husband whether the partnership firm was registered and whether the reconstitution of firm has taken place and registered in the Office of registrar of Firm as regards incoming and out going partner.
If the cheque issued to your husband is dishonored, in such event, your husband can institute a case u/s 138 of N I Act.
If the firm is not registered, then your husband can file a case against the firm before civil court .
I hope this clarifies your query. In case of any further assistance, feel free to communicate.