Thank you for the question.
As mentioned the filling was done a week ago, still pain and uncomfortale to chew may be because of a high point on the filling which is causing unequal distribution of the occlusal forces when you chew thus causing direct more pressure on the high point leading to pain.
one more reason could be the filling placed very to the pulpal horns which may lead to inflammation/involvement of the pulpal tissue of that tooth leading to toothache.this can be clarified by taking a radiograph of that particular tooth.
So high point can be corrected easily by a simple procedure. if pulplly involved then need to go for rooot canal tharapy after radiographic examination of pulp.you can consult your dentist
or an endodontist for this.
Nothing to woory about mouth watering it will reduce by its own within few days.this is because of the filling material which is a foreign object into the oral cavity leading to watering.
I hope i have tried to answer your query.