Hi Laoboi. . The lump could be from the GERD/acid reflux. It is important to get the GERD under control to prevent more damage. Do you know how to do this with dietary changes, enzymes and probiotics, all without OTC/prescription GERD meds?
The other thing the lump could be is post nasal drip possibly from allergies. GERD and allergies (whether from food or environmental) can cause sinus issues. Do you feel like you are constantly swallowing to get rid of the lump in your throat?
Try using OTC natural sinus remedies like Sinus Blaster (check online). Go to your local health food store or Whole Foods Market and ask a staff member in the vitamin department/Whole Body for help. Good luck to you.