hello anjani... according to details given by you i would presume you have some postural problems i.e. forward neck or stoop shoulder or improper worksatation which is causing you pain. if we think its rudimentary cervial rib you should have pain same or less in morning as muscle gets relaxed, but due to continous poor posture can cause pain spasm pain cycle hence it can mimic cervical rib pain. plz get yourself evaluated by local physical therapist. he will suggest you exercise.. mostly shoulder and upper back strenghtening and pain will be relieved... all the best