It sounds like your age spots were treated with cryotherapy (liquid nitrogen) which can unfortunately create a lot of discoloration (pigmentation alteration) from the treatment itself. Typically this discoloration resolves with time but is one of the reasons why I personally favor laser or chemical peeling for treatment of age spots. The fading process always takes longer in darker skin types. The best way to help improve the discoloration at this point is with topical bleaching agents such as hydroquinone and RetinA (topical tretinoin). Both of these should be prescribed and monitored by your dermatologist as they can be irritating and if used improperly, worsen the condition. Also make sure to be very careful with the sun.