What Could Be The Cause Of Bumps On Foot?

One of my staff has bumps / lumps on his foot. He was told they are bugs in his foot but it has been 6 months and he has been taking medication and they are not gone - but are worse. The skin on his foot is cracking off and he says it hurts. At one point his foot was really swollen - but not anymore. We aren't sure what it is. We live in Tanzania - so it could be a number of tropical diseases / infection / bugs. Please assist