angels,
If you have been diagnosed with thrush the lump could be a result of your immune system doing its job to combat the infection. Under your jaw runs a chain of submandibular lymphnodes that respond to inflammation and infection. A swollen lymphnode painful or not is a common result of the bodies reaction to oral thrush.
Gary stated it clearly, diflucan is the drug of choice with or without the subsequent administration of oral nystatin. If the lump goes away when the thrush is gone then it was just a normal process. If not ask your doc to evaluate the lump.
Try not to assume the worst, there are many non life threatening things that could cause this situation.
All the best,
Mike