The damage he's refering to is usually 4" in diameter and is caused by amonia is the urine not nitrogen. The chemical burn will break down in about a month. If the lawn is fertilized apply nothing. If not, applicating the lawn will help to mask the problem. Any additional burn will be undetectable. Fert will help the healthy grass creep back in that much faster.NickN said:NO,don't apply fertilizer.It will burn even more.The urea level of the dog is what burned the grass to begin with.You certainly don't want to add nitrogen to it.
If you have a rhizome spreading grass,apply generous amounts of water to the area,to dilute the urea,and let the grass fill in.
If you have a bunch type grass,you'll need to water heavily for a few days and then add seed or sod.