My cat has a hard lump under his chin?

Today I noticed that my cat has a pea to small marble sized hard lump under his chin. It does not seem squishy or movable. He recently, about a month ago, had a urethrostomy due to bladder problems and he and I just moved to a new home this weekend. He has been off all meds for about 4 weeks now and he is using a new food and water dish until I get his old ones from the old place. It seems like it may possibly bother him. He does not like me touching it but does not go berserk when I try. I want to take him to the vet but due to his surgery I have a rather larger vet bill and honestly have no money to pay for a visit and more lab work. What should I do and does ANYONE know what it could be? Oh and I don't think its an abscessed tooth because the vet has always said he had healthy teeth but I still won't rule it out yet! Please, please help!!! Thanks!!!