I'd be worried about tear or rupture of the clavicular head of the pectoralis muscle.
Injuries can occur at any point from the origin to the insertion and are graded based on the site and degree of the tear. A grade 1 injury is a contusion or strain without tearing. Grade 2 injuries are partial tears, usually of the muscle body or musculotendinous junction. Although grade 2 injuries produce less functional impairment than a complete rupture, the resulting weakness can considerably impair an active patient's ability to train and compete. Finally, grade 3 injuries are complete tears of the musculotendinous junction or an avulsion of the tendon.
Most complete tears involve an avulsion of the tendon from the humerus or arm bone but can also originate from the collar bone. Unfortunately, but not always the case, this is commonly seen with growth hormone use or anabolic use due to the rapidly changing muscle mass when a person uses anabolic steroids or growth hormone without the necessary tendon strength to accompany it.