Hematoma has not decreased in size its 4 month since the extraction of the tooth , the dentist told me to massage the hematoma now its getting bigger?

Probably not that: It can take longer than 4 months for a hematoma to completely resolve. Some turn into fibrous scar tissue that remains and will never go away. However, the fact that you state the area is not getting bigger (after 4 months) leads me to believe it is not a result of a hematoma, but more likely an infection or something else. Perhaps get a second opinion from another dentist

Get a second opinion: If it is getting larger in size .I think you should seek the help of another dr for second opinion. Do you have any medical problems?

Long time: Four months is a long time for the hematoma to still be present. I would get a second opinion.

Difficult...: Since it has been quite a while since your tooth was removed, and your healing of the wound is likely completed, it is not common that you continue to have hematoma. If too much pressure was applied, it may be spread wide, but that is unusual. Applying heat to facilitate drainage may be suggested, but this is not good for all cases. It's best to have the dentist examine the area to get proper care.