How long has the lump been there?
We could be dealing a wart type of growth.
They can become ulcerated-it is fine to apply a triple antibiotic ointment to the area twice daily.
He should be seen by a vet-as they can actually take a sample from the lump and lok under the microscope to get a better idea of what we rea dealing with. It may be able to be surgically removed. The gentomycin is fine to use. Warts can bleed.
The drinking more is a separate issue-in which his urine should be tested-as this could be a sign of diabetes.
Either medication is fine to use.
age can come with warts.
Diabetes is treatable, insulin shots daily-very easy to do!