The problem in inner thigh may be due to fungal infection
or due to bacterial. If you can upload the photo of the lesion we can better diagnose.
For now ask him to keep the area clean and dry, wear only loose fitting sun dried cotton inner wears, wash the area and dry it with compression but no rubbing. Use antiseptic (betadine
lotion) to clean the area. These will help him. Further management needs examination of the lesion and also peripheral area for any lymph
node enlargement and any other problem.
Hope this helps you.