The root canal filling was over-extended. This  is one of the unfortunate risks of having root canal therapy- and a risk that you take when under-going treatment. I would see how the tooth settles. It may be fine and you may experience no problems with it. If however, the tooth fails to setlle and becomes uncomfotable, then further treatment may be necessary- but I would wait firstly to see how it goes.
If you have any concerns with the treatemnt you have received, then you are always in your right to get a 2nd opinion from another dentist.
Thanks for your enquiry