It seems you overstressed yourself either with weight or may be you were in wrong posture during exercise which has lead to this problem which probably is due to the injury
to articulating ligaments. You need to see your doctor & Physiotherapist at the earliest so that rationale treatment could be started. You may need to get a few radiological investigations done like X-ray elbow.
Till then do not stress your affected arm/forearm/hand. use hot water bag fomentation and see your doctor for further line of treatment.
Wish you a speedy recovery to health