It is good you are noticing any changes to any moles or spots. As all have mentioned above, go into to see the doc to get it checked. They look at all three of these things to determine the safety of a mole or spot and is best checked by a physician.

The ABC's of the skin moles:
A-Asymetry
Symetrical (good) or if one half is equal in size to the other half is a suspect
B-Border
Border smooth (good) or if irregular/ragged/jagged/notched/scalloped/etc. shaped is a suspect
C-Color
Same color (good) or if there is more than one color is a suspect