How do I stop by dog licking its bum?

oh its a boy well my dog has just been in for an operation because she was licking the hole time allso she had this lump so i would check for one on your dog and so my mum took her to ask and she had an infection up there so they had to give her a hysterectomy aswell as the infection. shes on two sets of antiboticts and gets her ten stiches out in a week poor thing shes a 9 year old golden retrvier. alos she could of died if my mum never to her because it was speading. so i would just take your dog for a check up.