Can a crown with small hole in middle be filled ?

It can be filled: But more info is needed. Reason for the hole? Age of the crown? Condition of crown? These types of restorations are not quite like fillings in your teeth... These are more like a patch, and may not seal the defect adequately to prevent leakage and further decay. Your local dentist can take all of these factors and advise you if it's best to replace the crown.

Yes but.........: Yes, it is easy, quick and inexpensive to fill a small hole in the middle of the biting surface of a crown. However, there are some risks. First, the porcelain\ceramic may break during the drilling process. Second, it's basically a patch and it will not look as good nor be as permanent as the original crown. Third, make sure the rest of the tooth and crown are intact and fits well.