I was stocking the walkin cooler at work, and i came out all of a sudden, and instant pain and stiffness in my non dominant hand. there is no fever, loss of grip, and i cant make a fist?

Need to examine: It is not feasible to provide a meaningful opinion without additional history, physical examination and may be some tests. It would be prudent to see a doctor. You may start with the employee health department of your company and see if they will refer you to a neurologist. Wish you good health!

See neuro if lasts: A mew symptom of not being able to use one hand is worrisome hit a neurological process. It could be a sign that you are about to have a migraine headache. It could me muscle soreness from the loading you just did. If it does not improve in 1 hour, you should be seen at the ER to rule out stroke.