Do I need to pay estimated taxes on capital gains from the sale of equity from an acquisition?

Hello - 

 

My employer was bought recently, and the employees were paid out from out RSU's resulting in capital gains for the year. This happened in late December. I have heard two stories on how to go about paying taxes. 

 

Without the payment, I would be getting about $1500 back on my return this year. Do I need to estimate the taxes for the capital gains and pay those before the January 17th deadline?