Hello and welcome to HCM,
I have noticed that you have developed 
salivary gland swelling ( The site you mentioned, I think is Parotid) approx 12 days after 
tonsillectomy. With the history you have given, i can assume it to be 
parotitis. The medicine you are taking is OK, but in addition i always prefer an ORAL gurgle particularly "povidone iodine". Just after tonsillectomy your doctor might have been prescribed "Hydrogen Peroxide" gurgle to you, as many surgeon prefers, which helps a lot. 
In any resistant cases, a throat swab & culture will help to determine what antibiotics will be correct for you although there is maximum chances that it will come sterile as you are already on antibiotic.
Anyway, strictly maintain an 
Oral hygiene, that will help you to improve fast. I would also advise an 
multivitamin (Limcee is Vit C).
Thanks & Wish you an early recovery