Helmet head.

In future.. if this occurs, remove seed shell ASAP. leaving it on only slows growth and potentially damages the growth tip. hold and secure while leaving any tiny crack in seed (where tap root exited) accessible. pull / push depending on your orientation of the grip to slowly open it further. if holding it correctly, it will cause zero stress to the leaves, stem and roots. it will remain steady throughout process vs yanked around. So that hand holds it still without blocking 1/2 of shell that has to be pried away from other half. tweezers to hold it, and a toothpick to prod gently. If holding it steady, should be able to pry it open with very little stress to the rest of the plant and only applying pressure to the shell while the plant remains in a steady position. it is very easy to lose a cotyledon in this process. take your time. I wear reading glasses that are stronger than i normally need. it helps. A memberane can often remain around the cotyledons after you remove the shell. you can slide this off using the toothpick and gently pushing from base of cotys -- get it into slit between the leaves and gently push/slide the membrane off. Don't try to tear the membrane -- high risk of damaging cotyledons. If you can get the toothpick into that crevice near bas of leaves, it will easily slide the membrane off. may need to gently hold plant near top while doing this.. not the tweezers, lol, that might damage stem. gemtle loose grip at most -- only enough to hold it steady. cotyledons won't fully spread out immediately, but if seeming;y still 'fused' together when shell is removed, look closely for a membrane around it. should be able to get 'behind it' at the base of cotys and slide it off with very little force. How deep you plant the seed impacts how fast it can break ground but also the probability of the shell remaining on. So if this is common, try slgihtly deeper.. slightly would be millimeters deeper, not any significant distance. if it rarely happens, you are probably fine on depths.