The initial symptoms you describe may well be secondary to acute sinusitis, possibly secondary bacterial infection. The new development of “swelling of gums” is probably unrelated to your initial symptoms, (except to the extent that upper respiratory infection seems to predispose one to the development of these lesions) and consistent with what are called aphthous ulcers, but I cannot say with certainty that the two problems are unrelated. These sores are not a sign of a sinus abscess but raise the question. Depending upon what they prove to be should answer the question of what is going on.
I strongly suggest that you consult with your dentist regarding the mouth/gum lesions and if he/she is unable to provide a diagnosis and treatment, that you then consult with an ENT specialist.