In the early days you wouldn't want to do too much expressing as this will increase engorgement. The more milk that is extracted from the breast, the more milk you will make. You can try cold compress, or try expressing a little just to relief it a bit... Best is to feed baby frequently.
There's some info here on engorgement and how you can relieve it:
Engorgement | Australian Breastfeeding Association
It becomes better once your boobs know how much milk to make for baby