Sores on my dogs paw

I have an almost 7 year old Morkie and he’s been licking the same paw for a few days now. The first few days he had a slight limp but it has gone away since then. It seems like he has a sore on his paw from either biting/licking it so much or another unknown reason. Does anyone have any recommendations? I just took him to the vet last week for a different reason, so another trip isn’t really in my budget unless it’s extremely necessary.