If you're thinking about running a 50k, first off, kudos! That comes out to quite the distance in miles - 31 to be exact (so it is actually farther than both a half-marathon and a full marathon by quite a ways).
Races that cover a distance farther than a marathon typically fall into what are known as "ultra marathon" race distances. The first distance after a full marathon is a 50k, followed by 50 milers, 100k's and 100 milers, etc. Ultra-marathons are not for the faint of heart. A distance that covers that many miles can really put a strain on the body, mentally and physically. And training for an ultra-marathon takes quite a bit of time, dedication, and the exhaustion can easily become unbearable. In fact, a large majority of people who run ultra-marathons are professional athletes because training for them (just to cross the finish line) can be a full time job all on its own.
Starting off your running career with a much shorter distance like a 10k was smart, and congratulations for finishing! That is an accomplishment in-and-of itself! However, I wouldn't advise signing up for a 50k race just yet, unless you have ample time and energy to really dedicate to training to run and complete 31 miles. (And by that, I mean months of training with 5 to 6 workouts a week, and sometimes running twice a day. And with a calorie burn that high, it would be smart to work with a professional to make sure you're getting in enough fats, proteins, and carbohydrates each day to fuel your running. You'll need to eat. A LOT.)
Instead, aim to complete a half-marathon first. Most runners and experts agree that if you can run half of a half-marathon, you can run the whole thing. And if you've already ran a 10k (6.2 miles) then you can surely run 7.5 miles (which is half of a half-marathon) and thus you can probably run a whole half-marathon. In fact, if you put a few weeks of dedicated training, I bet you can run a half-marathon quite fast and strong!