I'm having the same problem myself but I was warned after the treatment that the area around the tooth would be sensitive and that I would probably need to take pain medication. I've also got pain where the injections went in to numb the tooth. It took about 30 minutes to drill through the old filling and the tooth so I hope it's just a reaction to that. The first night after the treatment, I was in quite a lot of pain but the day after was ok - today it's been a sort of niggly pain, not bad but enough to make me realise it's not quite right. Hopefully it'll subside and all will be well when the crown is fitted in 2 weeks.
Is the tooth that was prepped aching or a different tooth?