Nasty carbon jello on spark plug
 

Yesterday while driving my 2000 cavalier 2.2L I started to notice that acceleration seemed sluggish and it sounded like my engine was misfiring, shortly after the check engine light came on. P0301 Misfire in Cylinder #1. I park it for the night and pulled the spark plugs the next day. When I pulled the spark plug out of that cylinder this is what came out. I replaced the plugs and wiring and it runs fine now but should I be worried about future problems? I have never seen this before.