I woke up today with sore forearms and it feels difficult to grab thing with my thumb?

Compression palsy: It is possible that you laid on the forearm or leaned against it too long over night, causing a mild compression palsy (nerve is injured and so thumb does not work well). There is medical condition: saturday night palsy--a drunken person sleeping on the bench leaning on his arm all night, next day can't straighten wrist our because of nerve injury. If not better, consult doc. Good luck.