If you already sold the property, you owe the capital gains tax.
If this is investment property, you may be able to do a section 1031 "like kind exchange" which allows you to postpone paying gains tax on the sale. This must be set up in advance (which is why you can't take section 1031 if you already sold the property), and you may need the help of an accountant. And, this only postpones the tax. At some point, you will have to pay all the postponed capital gains tax (unless you die and leave the property to your heirs). Whether it is a good idea to postpone the gain will depend on what you think your present and future capital gains tax rates will be.
If this is personal property (a second home, you mom's old home, not used as a rental or for business) then you can't do a like-kind exchange and must pay the tax when you sell.
The provision @M-MTax referred to applied when you sold the home you lived in and bought a replacement home, and that was eliminated in 1997 I believe.
