What Causes Small Brown Spot On His Testicle?

my husband is worried about what can only be described as a small brown spot on his testicle. he says he only noticed it about a week ago. he cannot get an appoinmtment with his doctor for 2 weeks. any advice would be very much appreciated. thank you.husband is 49 years old 5' 9' and 12stone 7pounds in good general health.