Would a tooth be sore after a filling has fallen out and been refilled?

it happens often: The most common underlying reason for a filling to 'fall out' is due to a cavity. When decay threatens the normal health of a tooth, it can affect the pulp of the tooth or the nerve center. Keep in mind that decay doesn't have to touch the nerve- it only needs to penetrate deeply enough to hurt the nerve. A deep filling often exposes this exact problem. It's time to see your dentist again!

Yes: Normally you lost your old filling because of decay under it , so cleaning that decay before filing the tooth again might get closer to the nerve ( pulp ) getting the tooth a little more selective to cole and sweets for a few days and feel better afterwards