Hi welcome to health care magic forum,
Ear piercing after a year is least likely to get infected.
Forceful replacing smaller one with bigger one may get an extra pierce and got infected or it could be the bigger one had an allergic reaction
If the dark red bump is painful and discharging ,it could be an infection.
But if it is itching than it could be allergic reaction.
I would suggest you just take out the earring and apply a local ointment .
If no relief than see an ENT specialist
for a clinical examination.