The bad smell indicates that it is infected. The neopsorin and cleaning will help only temporarily. This cat is most likely going to need oral antibiotics. Depending on the type of infection it is, they will probably prescribe something like cephalexin 250mg dosing being weight based. You can try calling a local vet and ask them what they think before taking him anywhere. They might even call in a prescription for an antibiotic for you to a walmart or something (usually a $4 prescription) since you can't afford to take him in to get tests etc at this time. It never hurts to ask!
