Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concerns....
As per your complain in case if you are diagnosed with 
sinus infection then there is a possibility that sore throat is secondary to 
post nasal drip..
I would suggest you to take a course of antibiotics like 
Levofloxacin or 
Azithromycin, take Ibuprofen to relieve pain and inflammation do warm saine gargles and steam inhalations..
Chew Vitamin C pellet to boost your immunity and suck throat lozenges..
Avoid spicy and chilled foods and drink plenty of warm fluids..
Along with these remedies for sinus infection you can take steroid nasal sprays, saline irrigations,do warm compresses around the nose..
Take decongestant like 
Phenylephrine and mucolytics like Bromohexine..
Hope this information helps..
Thanks and regards.
Dr.Honey Nandwani Arora..