If it gets worse, then you might need to see a Vet. This could be what is called a Rodent Ulcer, or it could be a bug bite, or something else altogether. I'd keep an eye on it and if it bothers your furbaby, or gets worse, as I said, schedule a Vet visit.
And if you are using plastic food and water dishes, this is the right time to switch over to glass, stoneware, or metal, which doesn't harbor bacteria in little scratches!