What do you do if the head of a tick is still in dog?

The tick head is a foreign object that the body reacts to the way it would to splinter: redness and swelling, infection, sometimes the presence of pus. This is a process that will eventually--in most cases--force the object out. This process can be aided by digging the tick head out with a flame-sterilized needle and/or trying to grab it with tweezers.