Do you have any evidence to support your assertion that mass (not matter - the two concepts are related but not identical) can't be infinite? The only evidence we have so far is the law of conservation of mass, which rather does suggest the infinite existence of mass. At all times that mass has been observed, it has remained constant, in that no new mass appears to have appeared. The creation of mass never having been observed, there is no evidence that it is possible to create mass. If mass exists, as it does, and, so far as we know, it cannot be created, then it must necessarily have always existed.<quoted text>
Well matter can't be infinite, especially since it's not all powerful. God can be infinite(rather eternal).
Your god can be infinite or eternal, or anything else you care to define him/her/it as being. Since it is an imaginary being, it may possess any characteristics which you are capable of imagining.