Resigned, Not Served Notice period, denial of gratuity

Hi, I resigned on 16th August, so had to serve notice period till 16th sep. But due to medical emergency in home, I had to leave the job without serving the notice period, so left on 3rd Sep. The organization even tried relieving me, but due to some minor pending task, my no dues was not signed completely.Ans hence, it dint give me salary for that month as well. It is still pending. It dint relieve me,as I had some task pending to do. The college was affiliated to some state University. So I submitted my resignation there as well. And in January, I got a confirmation of relieveing from the state University which is basically done by the college itself. Then I asked for the gratuity. but the college is playing soft and harsh by stating that it is willing to give all but I have to go and completet that task. It's already an year, can an organization compel to do the task even when it is keeping the last month salary in lieu of the notice periodand also deny the gratuity? what legal action can be taken to get the gratuity? please help.