Can Phenylephrine Be Taken For Pain In Gums?

Hi, I have a tooth infection possibly/ probably with sinus involvement. Am on day 5 of an anti biotic, tooth feels better but I have an ache around the tooth in the gums probably from the sinuses. I have adult robitussin peak cold nasal relief in the house, it has phenylephrine 325 mg so I will try 2. The question I have is, should I or should I not take it with food.