I was at boxing training 4hrs ago & got hit quite hard on the left side of my head. My left eye hurts and decreased hearing in left ear. Should I worry?

Get checked. You don't have to lose consciousness to have suffered a concussion. Plus, it's possible that you have injuries such as a fractured facial bone, or bleeding behind the ear drum. I'd certainly get checked for these possibilities, and don't get back into the ring until you are cleared by a doctor. Good luck. Lgromkomd.