Chances are if what you say is swollen,I say buldging,it is popeye.Are there any other fish in the tank?You can either get a hospital tank for it,which is almost a have to have in this hobby,or flush it and get a new one.I would say get another tank.It doesn't deserve to die.Popeye is curable,but the medication you need for it is an antibiotic and could effect your cycle.Although,if you want to try to cure it you could use a med called macaryn.I'm not an expert on popeye so I can't be 100% on the effects of this medicine.But I know antibiotics can effect your cycle.Sometimes though with good water conditions it is possible for it to take care of its self.But during your initial cycle,its iffy.I'm sure someone else with more knowledge on popeye will help you.hth