I only replaced MRF tyre an year ago. It has cracks all over.

I replaced my super splendor's back tyre about an year ago. I have noticed that the tyre has cracks all around it. The MRF dealer said that it's not covered under warranty. I wanted to argue that they were only 1year old but, I realised that it's of now use. Should I replace them right away or can I use for few more kilometres?