I have a new white filling in a tooth. The tooth has become sensitive to temperature changes and pressure. What should I do?

This is a fairly common occurrence and the causes are probably related to the placement of the new filling. The tooth becomes hypersensitive because its vital soft tissue, located in the centre of the tooth, is in a pre-inflammatory state (pulpal hyperaemia). This condition develops due to irritation while removing tooth decay, which may have been very deep, or while removing an old filling. Drilling produces heat, vibrations..., and the procedure is certainly very invasive and can leave consequences for the tooth. The chemical processes involved in bonding and setting the filling may also further irritate the dental pulp. All of this can be partly avoided through working methods and the use of less invasive materials, but some harmful effect will always remain.
In any case, in your place I would try to tolerate it for a while if the pain is not too severe. Hypersensitivity to osmotic changes (sour, sweet, cold, hot, drying...) can be present for up to six months after the filling is made. If the tooth also becomes sensitive to biting or tapping, however, the situation is entirely different. In that case, return to your dentist.

I wish you a speedy improvement!