I don't care what the pharmacist says. Have it looked at by a doctor who practices medicine in that part of the world. I once ignored a sore not unlike that one, then came down with a walloping case of Lyme Disease -- and that was in the Temperate Zone. If you'd showed me that picture without giving me any further context, I'd have guessed it was a spider bite.

Tropical scrunges and rots come in a wonderful variety of forms. There are all kinds of viral and bacterial infections (some of them spread by insect bites), and recurrent funguses, and a bunch of slow-acting parasitic infestations I don't even want to think about. Get yourself checked out while you're still in the area. Don't wait until you'r back in the States, dealing with a doctor who wouldn't recognize this stuff if he saw it in a fully-labeled four-color photo insert.