Suggest Treatment For Nail Psoriasis

my son age 9 years is having nail psoriasis,first few months we consulted dermatologist he write salibet,no improvement dan we applied itchamol der was some improvement,than we consulted a consultant he told to apply canestan and one fourth tablet lamisil for 6 weeks but no response,lastly am using for my son diobet and calmuride, i want to ask whether this will be helpful to cure fully am really fedup and am worried all medicines are steriods am diabetic my son is also overweight his weight is 48kgs and height 137cm