The Incorrigible Night Owl

My cat Cosmo came up limping yesterday and it’s worse today. It appears there is a large bump on his leg, or perhaps it’s just swollen. He is also not acting himself, although he IS still eating and drinking. Robert is going to take him to the vet and drop him off, as we only have the one car till later in the week. I will be waiting to hear from them what is wrong.
He has never had any health problems before (he’s 9 years old!) He’s only been to the vet for shots. I’m kind of freaking out because, while I think it’s more likely it’s a sprain or a fracture, I am thinking of all these worst-case scenarios, like it’s a tumor or a break that will require surgery or something.
Aside from the worry over his health I am also a bit anxious about the vet bill. We WILL fix it, whatever it is…..but it would be really, really good if it was a fairly inexpensive problem.
Please think of Cosmo today! I will update when I have news.