That’s nasty! That’s both severe and traumatic! I would imagine lots of damage to surrounding muscles, tendons, and ligaments. Be patient!
That would explain it. Once you start moving, things will get better. The range of motion will come eventually. I remember when I was a kid and broke my arm. The cast included my elbow bent at 90 degrees. After about 3mo the cast was shortened to forearm only. My elbow felt like a rusty old joint w/no lube. Any elbow movement was both limited and painful, but it all came back in no time.