So about a week and a half ago, i went to fill up my gas tank. I accidentally forgot my gas cap. I suddenly realized about 5 minutes later and went back to find it. No good. I immediately drove to an auto supply store (about 3 miles) to get a replacement. Then just a few days ago, my check engine light comes on and i have a evap system large leak (not sure if they're related) and on top of that, i went to fill up my gas tank again, and a hissing sound like opening a bottle of soda came from behind the gas cap. Not sure if i should worry but i just wanted to be sure.