I am Dr Sriram nathan and I shall try to help you with your problem
In all probably you might have an infection in your throat and this would have caused your symptoms. The brown phlegm can be either due to an infection or a reflux.
None of these are to be worried. You can easily treat them and you can get back to normal in a week or so!
In any case you must do these:
1. Take warm water with a little salt and gargle
2. If you have pain then you must start a course of oral antibiotic like the amox-clav along with pain killers like the paracetamol
. Your doctor will know about this.
3. I would usually also start an anti reflux medication
like the pantoprazole
for a week or two
4. Avoid anything spicy and oily for the next one week or two
5. take voice rest for your throat and do not take anything cold
. Also do not have anything very hard.
6. You may also take an antihistamine medication like levocetrizine for a couple of weeks or so in consultation with your doctor.
You should feel better in a day or two. If not then you must consult an ENT surgeon to evaluate your tonsil
and throat. Also take a throat swab and get back to me or any ENT with the report.
hope this helps
Dr Sriram Nathan