Hi and thank you for your question.
Where is he licking?
What breed of dog do you have?
What have you tried so far?
Thank you for that information. I would check for any fleas first of all. If that is clean he could be licking out of pain , boredom or there is a hot spot possibly starting. What you will need to do is get an Elizabethan collar so he can't reach the area, if it is raw or reddened you will want to wash the area with antibacterial soap and then apply a triple antibiotic ointment to the area. It may be a hot spot so shaving the area down around the spot will help as they need to dry out to heal. Do the above with the ointment and washing several times a day.
An E collar can be found in any pet store or vet office.