I had pain from a crown and another filling last almost two weeks once, why, don't know for sure and had never had that reaction before. It was explained how sensitive nerves are sometimes and depending on how the nerve was touched and/or the reaction with the anesthetic used can aggrevate them. Even if the nerve was touching in the filing of the tooth can cause lasting discomfort and combined, the area needs time to heal. Also if there was infection present initially, there can be more pain and the procedure can initially aggrevate it but can clear up once rooted out but sometimes can get worse.

For me, it did go away though and have not had the reaction since. I suspect it was the injection that time and how the nerve was hit.

If concerned about gum infection, rinse with listerine and it will clear up many topical infections of the gums in the meantime.

If it persists, I would call back to get in or get another opinion and especially if you develop swelling in that area or fever, which is an indication of infection and definitely need to see them.