Apply ice pack but since you are unable to straighten the elbow since 2 days, show a physiotherapist who might diagnose a strain of the bicep or tendinitis or spasm. Please Refrain from overloading the muscles worst case scenario if the pain doesn't go down with physio treatment like release,ice pack for the muscle to relax , show an ortho because it may be a biceps tear diagnosed by an mri which needs rest or surgery.
Next Steps
show a competent physiotherapist but if situation doesn't improve show an orthopedic surgeon
Health Tips
do not do overloading ever. always train sensibly.