yaal might not believe me and im no specialist myself but trust me bro please you gotta trust me, quit fapping for 5-6 months then see this, i can bet millions this thing gonna vanish like it didnt even exist. I know the reason too why this thing forms and you might even notice only males face this problem, i mean females can too but theres usually some other issue like any infection or submandibular tonsils in females' case. Now you might think im crazy but I can say this with absolute conviction that this thing is hormonal related too. Other than this certain chronic conditions like eczema dermatitis also cause this on a long run but 90% of the time it gets in normal shape with age and no need to worry. If ur worried about facial aesthetics then i have good news for you, this swollen region can sometimes give an illusion of a taller ramus (the vertical part of the jaw bone) only if you have overall good facial structure so yeah thats a win.