Hi there, sounds like an unpleasant experience hopefully it won't be so bad next time. To treat bad hypos you need fast sugars. Best thing is glucose tablets, but jelly babies and sugary drinks also work. Chocolate is slow to enter your blood because of the fat content, and if your sugar levels are falling fast it can make a real difference. Bread is fast too, but you need to chew it to break the starch bonds and not put butter and cheese on it.
The pain could be anything, so if it is bad it's probably best to have it looked at. I've never had anything like that from a hypo. Hope you feel better soon.