Painless and immobile submandibular lump

Hello, I'm female 22. Recently, I noticed a painless lump on my left submandibular gland. I do not have any history of drinking, smoking, alcohol, etc. On December 5, while checking my gums from the recent tooth extraction, I noticed a painless and immovable lump on my left submandibular gland. I wasn't able to feel that lump until that day. At first we thought that it might just be related to the recent tooth extraction but was confirmed not after checking for infections which showed no signs and after taking antibiotics for 10 days straight which didn't clear the lump. It was still there up until now. I experienced some super dry throat and sore throat to a point that even drinking water feels so painful during month of October since I am a pratice teacher and  use my voice everyday day. A week after I noticed the lump, I also suffered from dry cough and itchy throat feeling the need to swallow all the time. Now all the symptoms were gone expect this lump.