Thanks for the query..
As per your complain discomfort in throat along with brown spots seems to be due to throat infection
leading to Granular Pharyngitis
and soreness and redness in lips and mouth seems to be due to Stomatitis
caused due to throat infection..
Nothing to worry as the condition is treatable and you can consult an ENT expert and get evaluated and a throat swab culture can help in confirmation of cause..
-You can be given antibiotics like Augmentin
along with anti-inflammatory painkiller like Ibuprofen..
-You should do warm saline gargles..
-You can gargle with numbing mouthwash containing Lignocaine...
-You can also take Vitamin B complex supplements to relieve mouth inflammation..
-Avoid spicy foods..
-Drink plenty of water..
Hope this information helps..