Hi! Since how many days you are having this problem. Probably you overstretched or hurt yourself during the workout.
If it is acute stage and it is very pain you can apply cold packs take rest the pain will go with in few days.
If this has become chronic you should not ignore and get it evaluated by Physiotherapist who can guide you the proper management.
Next Steps
Stop weight lifts and give time to heal and strengthen your muscles by physio exercises
Health Tips
Be slow and know your pace. Never compete with anyone in anyone during the workout . Compete with yourself