So horrible i cant eat any food. Need to fix now
Run around the big end with a conventional can opener (a P38 type will work best for the short radius corners).
I saw a video once of opening a can by rubbing the top on an abrasive surface - cement floor, for example - you wear down the edges where the top is sealed to the bottom and eventually you can peel off the top. I'd say this is a hard way to go, you have to be pretty hungry to use this method - it was a survival method, not for routine use.