Oh man. Common sense would tell one that if one's arm was tensed up and whatnot from working out and wouldn't extend properly while in a resting position, sleeping with it bent is not a good idea. However, I have no common sense, and thus I woke up to extreme pain if I tried to unbend my arm. xP Dammit.
Gonna go take a hot shower and try to work it out there, cuz doing it here isn't working, and the heat would propably help.
edit: Well, that helped some. The last stretch still hurts, but hopefully, that'll unkink on its own.