Getting inside these early cans was more of a victory than a routine. In fact, food cans were often reused as cooking pots, and sometimes came with handles for that purpose.
Eventually, in the 1850s, specialized tools known as "can openers" started to appear on the market. Even then, they generally weren't sold to the public, because they were typically considered too dangerous for them to be trusted with. Grocers would use them to open canned goods upon purchase, which kind of defeats the purpose of buying canned goods in the first place.
"Sorry, Timmy. You can't be trusted with this dangerous can opener. Now get on back down the coal mine."
The can opener we know today was invented by William Lyman in the 1870s, and was only released to the market when we as a society decided that we could probably operate a simple hand-cranked machine without severing our own arteries.