Can post nasal drip cause the tonsils to be red and some soreness? runny nose, sinus headache, and tonsil area red and sore. thanks :)

Yes: May be a vital illness or less likely bacteria. I would gargle and take OTC cold meds but if the throat is worse get a culture done

Not usually: Post-nasal drips do not affect the tonsils. With the cluster of symptoms , you need to rule out the presence of sinusitis. Absent that, acid reflux may affect the lingual tonsil (that one which sits behind your tongue and not usually visible) and occasionally the oropharyngeal tonsils if the reflux reaches as high as your mouth. See ENT.