Is it a very large or deep wound? We generally use alamycin spray it's an antibiotic so prevents infection /treats any that may be present. You do generally need a prescription from the vet but many places sell it without one ,just depends on the retailer . Alot of vets don't seem to worry about the spray as it is just a topical application. We find it only needs to applied twice a day for a couple of days.Alternatively you could use a cream intended for humans called ANTIPEOL it is used in hospitals to treat all sorts of skin problems . It all depends how friendly your pigs are ie not then spray , are then cream. Cream can be bought in most chemists although some wont know what you are talking about.