if it stays green-ish, even if you damaged the growth tip, it will eventually regrow. if you lost the growth tip it will take a long time and possibly fail, too.
losng 1 cotyledon isn't optimal, but the plant can survive that easily. Again, it'll be a bit slower early on due to less photosynthesis, but within a week or two it'll be inconsequential.
doesn't look shriveled, so the vascular tissue must be somewhat still connected. may not even lose the coty.
when you remove a shell, use some tweezers to hold it firmly. this reduces any stress on the stem / cotys. Use a toothpick or similar to gently pull/pry while you hold the seed shell steady. somtimes there's a membrane left behind. gently sliding toothpick along where the cotys pull apart can easily slide off a membrane without damaging anything. try to do these things without moving/agitating the seedling. hold it stead, press down on opeing to further pry shell wider until it can pop off. it shouldn't jostly the plant at all if holding it steady with tweezers.